Multi-electrode electrochemical cell and method of making the same

ABSTRACT

A multi-electrode device that includes an anode electrode, a cathode electrode, and a gate electrode situated between the anode and cathode, and having an electrolyte. The multi-electrode device can be a secondary (rechargeable) electrochemical cell. The gate electrode is permeable to at least one mobile species which is redox-active at at least one of the anode and cathode. The gate electrode has a resistance that is lower than that of a conductive non-uniform morphological feature that could be grown on the anode. The gate electrode provides the ability to avoid, recognize, and remove the presence of such non-uniform morphological features, and provides an electrical electrode that can be used to remove such non-uniform morphological features.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S.provisional patent application Ser. No. 62/020,337, filed Jul. 2, 2014,which application is incorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to electrochemical cells in general andparticularly to an electrochemical cell having more than two electrodes.

BACKGROUND

High capacity and reliability secondary (rechargeable) electrochemicalcells and batteries are pivotal to improving mobile electronics, and arebecoming more important in transportation and energy storageapplications as batteries take on more prominent roles in these realms.Key chemistries in current commercial secondary cells, and the batteriesconstructed from those cells, include Li-ion, lead-acid (Pb-acid),nickel-metal-hydride (NIMH), and Zn-air.

Mg based secondary cells, whether based on metal or other electrodetypes, are now emerging as a potential improvement upon existing celltypes for increased gravimetric and volumetric energy-density. Mg cellsare expected to approach 500 Wh/Kg versus Li-ion's 250 Wh/Kg. Similarly;Mg cells are expected to approach 1600 Wh/L versus Li-ion's 800 Wh/L.Moreover, magnesium is the eighth most abundant element on Earth, and ismuch less rare than lithium. At the same time, magnesium is easier andsafer to handle and can be incorporated in cells using the same orsimilar manufacturing techniques as cells using lithium. An importantclass of problems in the development of all of these cells arises frominability to control the ongoing evolution of cell morphology andpotential-distribution that occurs during charge-discharge cycleswherein electrochemically active species are redistributed throughout anelectrochemical cell. In particular, anodes such as those employed inMg, Pb, Li, and Zn-air cells can suffer from the development ofnon-uniform morphology during electrochemical cycling of the anode.Non-uniform morphologies variously referred to as dendrites, whiskers,asperities, and the like, can create immediately destructive andhazardous internal short circuits if they grow large enough to create anelectrical connection between the electrodes of an electrochemical cell.This problem particularly plagues the cycle life of all metal-anodecells and, despite the potential benefits of metal electrodes, has ledthe industry to employ non-metal electrodes in many commonly used celltypes to minimize these problems, even though non-metal electrodes donot completely eliminate these problems. Non-uniform morphologies alsocause longer term capacity fade through two related processes: First,the creation of a high-surface-area interface between an electrode andelectrolyte that forms massive amounts of decomposition productscommonly-termed “solid electrolyte interphase” through parasitic, orunintended, reactions with the electrolyte. In the case of Li metalanodes, these side reactions of the electrolyte form “mossy Lideposits.” Second, the stripping cycle of the cell can leave finelydivided, but electrically-isolated metal (known as the “dead lithium”problem in Li-metal technology development) distributed between theelectrodes. Moreover, imbalances in the amount of active electrodematerial of the positive electrode relative to the amount of activeelectrode material in the negative electrode can also increaseaccumulations of undesirable metal or metal compounds. Consequently,rechargeable batteries can suffer such unfortunate events as thermalrunaway, cell rupture, catching fire or even exploding if subjected tothe wrong electrical or thermal conditions.

One approach, which is the dominant approach today, is to simply avoidthe use of metallic electrodes altogether, by constructing electrodesoperating as intercalation hosts, or alloying, conversion, anddisproportionation reactions. This technique aims to eliminate a directmetal surface at the cost of energy density of the cell. Nevertheless,the use of intercalation hosts, or alloying, conversion, anddisproportionation reaction materials results in a cell that may stillultimately deposit metal on an electrode surface under certainconditions of operation. Moreover, avoiding the use of metal anodeswould very likely prohibit the implementation of Mg cells, now widelyrecognized as one of the most promising next-generation chemistries formoving beyond Li-ion batteries.

Another approach to preventing degradation of metallic electrodes hasbeen to provide an ionically conductive, but electrically insulatingcoating such as a ceramic or polymer on the surface of the electrodethat contacts the electrolyte. However, this approach will fail if evensmall imperfections in the coating exist, and the electrolyte can makedirect contact with the electrode. Moreover, although there have beenclaims in the literature that certain coatings prevent surface plating,laboratory measurements presented below indicate that these claims arenot reproducible, and surface plating that would lead to non-uniformmorphological features occurs on the coating, obviating its utility.

The vast majority of electrochemical cells have only two electrodes: acathode and an anode. However, a third passive “reference” electrode iswell-known in the field and is widely used in both lab cells andcommercial cells for monitoring purposes. These reference electrodes aremanaged so as to have no effect on the operation of the cell, and playno role in maintaining the performance of the cell. Since its role is tomonitor cell electrochemistry, rather than to drive significant current,this reference electrode is generally much smaller than the two “workingelectrodes,” covering only a small portion of the active area of thecell. To limit any possible influence or interference with the workingelectrodes reference electrodes frequently lie outside the stack ofcathode/separator/anode while maintaining ionic contact with theelectrolyte. Similarly, in order to accurately measure cell performancewithout interacting with the working electrodes, the currents passedthrough a reference electrode typically lie in the range of 1-1000 ppmof the current through working electrodes.

In addition to the use of reference electrodes, there have been severalproposals for third electrodes in the cell, several of which arediscussed below.

Known in the prior art is Werth, U.S. Pat. No. 4,349,614, issued Sep.14, 1982 (also published as European Patent Application Publication No.EP0060642 on Sep. 22, 1982), which is said to disclose an auxiliaryelectrode of platinum or palladium that is immersed in the electrolyteof a lead-acid battery and connected to the negative plate of thebattery so that, when the battery is employed in float service, hydrogenevolves on the auxiliary electrode whereby the parasitic currentequivalent to the hydrogen evolution increases the float current to thepositive plate of the battery.

Also known in the prior art is Morris, U.S. Pat. No. 5,585,206, issuedDec. 17, 1996, which is said to disclose electrode sections, such asanode and cathode sections, of a battery cell that include currentcollectors with exposed portions. The exposed portions contain slitswhich form tabs. These tabs can be spot welded together to formconnections between the electrode sections.

Also known in the prior art is Li et al., U.S. Pat. No. 5,688,614,issued Nov. 18, 1997, which is said to disclose an electrochemical cellprovided with first and second electrodes, and a solid polymerelectrolyte disposed therebetween. The electrodes may either be of thesame or different materials and may be fabricated from ruthenium,iridium, cobalt, tungsten, vanadium, iron, molybdenum, halfnium, nickel,silver, zinc, and combinations thereof. The solid polymer electrolyte isin intimate contact with both the anode and the cathode, and is madefrom a polymeric support structure having dispersed therein anelectrolyte active species. The polymer support structure is preferablya multi-layered support structure in which at least a first layer isfabricated of a polybenzimidazole, and at least a second layer isfabricated of, for example, poly vinyl alcohol.

Also known in the prior art is Maloizel, U.S. Pat. No. 6,002,239, issuedDec. 14, 1999, which is said to disclose a cell charging voltage adaptercircuit, and a battery including such a circuit external to the cell andcell stack assembly, wherein the charging circuit includes terminals ofresistor between one of the connecting terminals and one of the outputterminals and a comparator between the connecting terminals and adaptedto control the variable resistor in accordance with the results ofcomparing the voltage between the connecting terminals and a nominalvoltage.

Also known in the prior art is Meissner, U.S. Pat. No. 6,335,115, issuedJan. 1, 2002, which is said to disclose secondary lithium-ion cellswhich include at least one lithium-intercalating, carbon-containingnegative electrode, a nonaqueous lithium ion-conducting electrolyte andat least one lithium-intercalating positive electrode including alithium-containing chalcogen compound of a transition metal, theelectrodes being separated from one another by separators. Alithium-containing auxiliary electrode is disposed in the cell tocompensate for the irreversible capacity loss in the secondarylithium-ion cell.

Also known in the prior art is Zhong, U.S. Pat. No. 6,383,675, issuedMay 7, 2002, which is said to disclose a third electrode for use in ametal-air tricell comprising a support structure coated with a layer ofa lanthanum nickel compound and at least one metal mixture, wherein themixture is adhered to the support structure without the use of anadhesive. In another embodiment, the Zhong invention relates to ametal-air tricell comprising: an air electrode; a metal electrode; and athird electrode, wherein the third electrode comprises a supportstructure coated with a mixture of a lanthanum nickel compound and atleast one metal, wherein the mixture is adhered to the support structurewithout the use of an adhesive. Additionally, the Zhong invention alsorelates to a method of forming a third electrode for use in a metal-airtricell comprising the steps of: (A) applying a mixture of a lanthanumnickel compound and at least one metal oxide to a support structure,thereby yielding a coated support structure; and (B) heating the coatedsupport structure in order to reduce the metal oxide present in thelanthanum nickel compound/metal oxide mixture to its corresponding metaland to adhere the mixture to the support structure, thereby yielding athird electrode wherein the third electrode is free of an adhesive.

Also known in the prior art is Slezak, U.S. Pat. No. 6,869,727 issuedMar. 22, 2005, which is said to disclose an electrochemical battery cellhaving a high electrode interfacial surface area to improve high ratedischarge capacity, where the shapes of the electrodes facilitate themanufacture of cells of high quality and reliability at high speedssuitable for large scale production. The interfacial surfaces of thesolid body electrodes have radially extending lobes that increase theinterfacial surface area. The lobes do not have sharp corners, and theconcave areas formed between the lobes are wide open, to facilitateassembly of the separator and insertion of the other electrode into theconcave areas without leaving voids between the separator and eitherelectrode.

Also known in the prior art is Wang et al., U.S. Patent ApplicationPublication No. 2007/0141432 A1, published Jun. 21, 2007, which is saidto disclose a third electrode frame structure for use in a fuel cell orbattery is provided. The third electrode frame structure may include afirst electrode, a separator positioned on an outer perimeter of thefirst electrode, and a frame third electrode coupled to the separator.The separator may be positioned in a same plane between the firstelectrode and the third frame electrode.

Also known in the prior art is Christensen et al., U.S. Pat. No.7,846,571, issued Dec. 7, 2010, which is said to disclose a lithium-ionbattery cell which includes at least two working electrodes, eachincluding an active material, an inert material, an electrolyte and acurrent collector, a first separator region arranged between the atleast two working electrodes to separate the at least two workingelectrodes so that none of the working electrodes are electronicallyconnected within the cell, an auxiliary electrode including a lithiumreservoir, and a second separator region arranged between the auxiliaryelectrode and the at least two working electrodes to separate theauxiliary electrode from the working electrodes so that none of theworking electrodes is electronically connected to the auxiliaryelectrode within the cell.

Also known in the prior art is Roh et al., U.S. Patent ApplicationPublication No. 2011/0217588 A1, published Sep. 8, 2011, which is saidto disclose a secondary battery which includes an electrode assemblycomprising inner stacked electrodes and at least one outermost electrodepositioned on at least one end of the inner stacked electrodes; and acase configured to house the electrode assembly. The at least oneoutermost electrode comprises an inactive material.

Also known in the prior art are a range of techniques for the use of anadditional electrode to monitor cell chemistry. For example, Kaneta etal., U.S. Pat. No. 8,017,260, issued Sep. 13, 2011, is said to disclosea secondary battery in which temperature rise (heat generation) can bemeasured accurately at the time of quick charge/discharge, and a batterywhich can be configured readily using the secondary batteries whilerealizing low resistance. Separately from the positive and negativeelectrode terminals of a flat laminate film secondary battery, a thirdterminal is fixed perpendicularly thereto. The third terminal isconnected with the electrode current collecting parts of a powergenerating element body constituting the secondary battery (1) andimparted with a potential equal to that of any one of the positive andnegative electrode terminals. Inner temperature of the secondary batteryis determined by measuring the temperature of the third terminal and acell balancer circuit, or the like, is connected with the thirdterminal. The battery is configured by connecting the positive andnegative electrode terminals directly in series.

Also known in the prior art is Ramasubramanian et al., U.S. Pat. No.8,119,269, issued Feb. 21, 2012, which is said to disclosethree-dimensional secondary battery cells comprising an electrolyte, acathode, an anode, and an auxiliary electrode. The cathode, the anode,and the auxiliary electrode have a surface in contact with theelectrolyte. The anode and the cathode are electrolytically coupled. Theauxiliary electrode is electrolytically coupled and electrically coupledto at least one of the anode or the cathode. According toRamasubramanian, electrically coupled means directly or indirectlyconnected in series by wires, traces or other connecting elements. Theaverage distance between the surface of the auxiliary electrode and thesurface of the coupled cathode or the coupled anode is between about 1micron and about 10,000 microns. According to Ramasubramanian, theaverage distance means the average of the shortest path for ion transferfrom every point on the coupled cathode or anode to the auxiliaryelectrode.

Also known in the prior art is Roumi, U.S. Patent ApplicationPublication No. 2013/0224632 A1, published Aug. 29, 2013, which is saidto disclose separator systems for electrochemical systems providingelectronic, mechanical and chemical properties useful for a variety ofapplications including electrochemical storage and conversion.Embodiments provide structural, physical and electrostatic attributesuseful for managing and controlling dendrite formation and for improvingthe cycle life and rate capability of electrochemical cells includingsilicon anode based batteries, air cathode based batteries, redox flowbatteries, solid electrolyte based systems, fuel cells, flow batteriesand semisolid batteries. Disclosed separators include multilayer, porousgeometries supporting excellent ion transport properties, providing abarrier to prevent dendrite initiated mechanical failure, shorting orthermal runaway, or providing improved electrode conductivity andimproved electric field uniformity. Disclosed separators includecomposite solid electrolytes with supporting mesh or fiber systemsproviding solid electrolyte hardness and safety with supporting mesh orfiber toughness and long life required for thin solid electrolyteswithout fabrication pinholes or operationally created cracks.

Also known in the prior art is Noguchi, Korean Patent No. 1013754220000,issued Mar. 17, 2014, which claimed priority to Japanese PatentApplication 2009/281122 through WO 2011/070712 A1, published on Jun. 16,2011, which is said to disclose the following: Provided is a lithium-ionbattery wherein internal short-circuits that are caused by inclusion ofmetallic foreign matter can be detected early with high sensitivity.Also provided is a method for producing the same. The lithium-ionbattery, which is provided with a positive electrode (16), a negativeelectrode (15), and an electrolyte, is further provided with an electricinsulating layer (3) which is between the positive electrode and thenegative electrode and comprises an electro conductive layer (4). Byapplying a voltage between the positive electrode (16) and theelectroconductive layer (4), and measuring a current and a potentialdifference between the positive electrode (16) and the electroconductive layer (4), the possibility of the occurrence of internalshort-circuits in the lithium-ion battery can be detected early withhigh sensitivity since there is an earlier occurrence of a short-circuitbetween the positive electrode and the electroconductive layer thanbetween the positive electrode and the negative electrode.

Also known in the prior art is Cui, et al., U.S. Patent ApplicationPublication No. 2014/0329120 A1, published Nov. 6, 2014 (simultaneouslywith Cui, et al., WO 2014/179725 A1), which is said to disclose abattery that includes: 1) an anode; 2) a cathode; 3) a separatordisposed between the anode and the cathode, wherein the separatorincludes at least one functional layer; and 4) a sensor connected to theat least one functional layer to monitor an internal state of thebattery.

There is abundant recognition that the presence and the formation ofnon-uniform morphological features is one of the most serious problemsin electrochemical cells, and particularly so in the compact batteriesemployed in devices such as mobile phones, grid-communication systems,distributed telemetry systems, tablet computers, laptop computers,backup-power systems, cameras, aerial drones, alarm systems, firedetection systems, personal fitness sensors, power tools, electronicinstruments, musical instruments, aircraft, automobiles, satellites andmany other devices with similar requirements. Unfortunately, there hasbeen very little progress in managing non-uniform morphological featuresfor such cells. Indeed, the primary driver for the adoption ofintercalated electrodes is to suppress the formation of non-uniformmorphological features, but the adoption of such electrodes comes at thecost of energy density.

In addition, it is well known in the field that non-uniformmorphological features are a common failure mode even in cells utilizingintercalated electrodes. Specifically it is known that in Li-ion cellswhere the anode incorporates Li at a potential close to the Limetal-plating potential (including but not limited to anodes comprisinggraphite, silicon, or tin), non-uniform morphological features may formdue to low-temperature cycling, excessive charging (either to too highpotentials, or too rapidly) or a combination (see Adam Heller, The G. S.Yuasa-Boeing 787 Li-ion Battery: Test It at a Low Temperature and KeepIt Warm in Flight, The Electrochemical Society Interface Summer 2013,page 35, Published online Mar. 25, 2013, for example). Thus the risk ofnon-uniform morphological features is known to be a prime limiter ofperformance in normal intercalation-anode Li-ion batteries, specificallylimiting charging profiles, charging rates, and temperature windows foroperation.

A more general description of some of the deleterious effects ofdeposition of metal or other material is that an anode electrode orcathode electrode can become distorted or changed in shape from thedimensions of the electrode that were originally provided in thebattery, e.g., asperities or other changes resulting in non-uniformmorphological features or dimensions of the electrode, can negativelyimpact the good operation of the battery.

There is a need for systems and methods that can control the undesiredevolution of morphological changes of electrodes.

SUMMARY OF THE INVENTION

Taken as a whole, the present disclosure opens the door for a longsought need, and commercially valuable goal: the ability to use eithernon-metallic or metallic working electrodes (or electrodes that operateclose to the metallic potential) in compact secondary cells thatcontinue to operate for extended numbers of charge-discharge cycleswithout being damaged by the evolution of non-uniform electrodemorphology.

According to one aspect, the invention features a device comprising: acathode electrode having a cathode electrical terminal, the cathodeelectrode in electrochemical communication with an electrolyte; an anodeelectrode having a anode electrical terminal, the anode electrode inelectrochemical communication with the electrolyte; at least one gateelectrode having a gate electrode electrical terminal, the at least onegate electrode in electrochemical communication with the electrolyte andpermeable to at least one mobile species which is redox-active at atleast one of the anode electrode and the cathode electrode, the at leastone gate electrode situated between the cathode electrode and the anodeelectrode; and a control circuit configured to actively control anoperating parameter of the device.

In one embodiment, the control circuit is configured to set a voltage ofthe at least one gate electrode relative to at least one of the anodeelectrode and the cathode electrode at a predetermined voltage value.

In another embodiment, the predetermined voltage value is sufficient tostrip plated metal derived from the at least one mobile species.

In yet another embodiment, the predetermined voltage value is aformation potential of a non-uniform morphological feature.

In still another embodiment, the control circuit is configured tomaintain a current between the at least one gate electrode and the anodeelectrode to be less than a threshold current.

In another embodiment, the control circuit is configured to control aflow of current through the device based on one of a voltage, animpedance and a current measured between the at least one gate electrodeand at least one of the anode electrode and the cathode electrode.

In a further embodiment, the device is a secondary electrochemical cell.

In yet a further embodiment, the at least one gate electrode has aplanar geometry defined by a thickness dimension and a two dimensionalarea perpendicular to the thickness dimension.

In an additional embodiment, the at least one gate electrode isionically conductive along the thickness dimension and is electricallyconductive perpendicular to the thickness dimension.

In one more embodiment, an impedance measured at a frequency less than 1Hertz between any two points on a two dimensional area perpendicular tothe thickness dimension of the at least one gate electrode is less than1 MegaOhm.

In still a further embodiment, the anode electrode is a metal anode.

In one embodiment, the metal anode is Magnesium or an alloy containingMagnesium.

In another embodiment, the metal anode comprises a metal or an alloycontaining a metal selected from the group of metals consisting of Zinc,Calcium, Aluminum, Lithium, Sodium, and Lead.

In yet another embodiment, the anode electrode is an anode electrodeselected from the group consisting of a conversion anode, anintercalation host, an alloying reaction anode and a disproportionationreaction anode.

In still another embodiment, the redox-active ionic species is lithiumand the anode comprises a material selected from the group of materialsconsisting of crystalline carbon, amorphous carbon, Na, K, Rb, Cs, Be,Mg, Ca, Sr, Al, Si, Ge, Sb, Pb, In, Zn, Sn, and binary Me-×compoundswherein X is selected from the group consisting of sulfur, phosphorous,nitrogen and oxygen, and Me includes a metal selected from the groupconsisting of Mg, Ca, Sr, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni,Cu, Ag, Zn, Cd, B, Al, Si, Sn, Ge, Sb, Bi and a combination thereof.

In a further embodiment, the anode electrode is configured to operateunder plating conditions based on the temperature, voltage,charging-rate or combination thereof.

In yet a further embodiment, the at least one gate electrode comprises aselected one of an electronically conducting material as freestandingform and an electronically conductive film deposited upon an insulatingsubstrate having porosity and tortuosity, and connected to externalcircuit through a dedicated tab.

In an additional embodiment, the at least one gate electrode hasporosity sufficient to maximize the efficiency of the permeability tothe at least one mobile species.

In one more embodiment, the at least one gate electrode has porosityhaving sufficient tortuosity to minimize the probability that anon-uniform morphological feature projecting through the at least onegate electrode fails to make electrical contact to the at least one gateelectrode.

According to another aspect, the invention relates to a secondaryelectrochemical cell having a cathode electrode having a cathodeelectrical terminal, the cathode electrode in electrochemicalcommunication with a electrolyte and an anode electrode having a anodeelectrical terminal, the anode electrode in electrochemicalcommunication with the electrolyte; wherein the improvement comprises:at least one gate electrode having a gate electrode electrical terminal,the at least one gate electrode in electrochemical communication withthe electrolyte and permeable to at least one mobile species in theelectrolyte which is redox-active at at least one of the anode electrodeand the cathode electrode, the at least one gate electrode situatedbetween the cathode electrode and the anode electrode; and a controlcircuit configured to actively control an operating parameter of thedevice.

According to still another aspect, the invention relates to a method ofmaking an electrochemical device. The method comprises the steps of:providing a cathode electrode having a cathode electrical terminal;providing an anode electrode having a anode electrical terminal;providing an electrolyte in in electrochemical communication with thecathode electrode and the anode electrode; providing at least one gateelectrode having a gate electrode electrical terminal, the at least onegate electrode in electrochemical communication with the electrolyte andpermeable to at least one mobile species in the anode electrode which isredox-active at at least one of the anode electrode and the cathodeelectrode, the at least one gate electrode situated between the cathodeelectrode and the anode electrode; and providing a control circuitconfigured to actively control an operating parameter of the device.

According to a further aspect, the invention relates to a method ofoperating an electrochemical device. The method comprises the steps of:providing a cathode electrode having a cathode electrical terminal;providing an anode electrode having a anode electrical terminal;providing an electrolyte in in electrochemical communication with thecathode electrode and the anode electrode; providing at least one gateelectrode having a gate electrode electrical terminal, the at least onegate electrode in electrochemical communication with the electrolyte andpermeable to at least one mobile species in the anode electrode which isredox-active at at least one of the anode electrode and the cathodeelectrode, the at least one gate electrode situated between the cathodeelectrode and the anode electrode; providing a control circuitconfigured to actively control an operating parameter of the device; andoperating the electrochemical device such that the control circuitmaintains the operating parameter of the electrochemical device in acondition of normal cell health.

According to one aspect, the invention features a device comprising: acathode electrode having a cathode electrical terminal, the cathodeelectrode in communication with an electrolyte; an anode electrodehaving a anode electrical terminal, the anode electrode in communicationwith the electrolyte; at least one gate electrode having a gateelectrode electrical terminal, the gate electrode in communication withthe electrolyte and permeable to at least one mobile species which isredox-active at least one of the anode and the cathode, the gateelectrode situated between the cathode electrode and the anodeelectrode; and a stripping circuit configured to apply a current to thegate electrode sufficient to strip a non-uniform morphological featurethat is electrically connected to either of the cathode electrode andthe anode electrode.

In one embodiment, the gate electrode has a planar geometry defined by athickness dimension and a two dimensional area perpendicular to thethickness dimension.

In another embodiment, the anode is a metal anode.

In yet another embodiment, the metal anode is magnesium or an alloycontaining magnesium.

In still another embodiment, the metal anode comprises a metal or analloy containing a metal selected from the group of metals consisting ofzinc, calcium, aluminum, lithium, sodium, and lead.

In a further embodiment, the anode has a reaction voltage that lieswithin 0.1V to 1.2V of the non-uniform morphological feature formationpotential.

In yet a further embodiment, the anode is a conversion anode.

In an additional embodiment, the anode is an intercalation host.

In one more embodiment, the anode is an alloying reaction anode.

In still a further embodiment, the anode is a disproportionationreaction anode.

In one embodiment, the redox-active ionic species is lithium and theanode comprises a material selected from the group of materialsconsisting of crystalline carbon, amorphous carbon, Na, K, Rb, Cs, Be,Mg, Ca, Sr, Al, Si, Ge, Sb, Pb, In, Zn, Sn, and binary Me-×compoundswherein X is selected from the group consisting of sulfur, phosphorous,nitrogen and oxygen, and Me includes a metal selected from the groupconsisting of Mg, Ca, Sr, Ti, Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni,Cu, Ag, Zn, Cd, B, Al, Si, Sn, Ge, Sb, Bi and a combination thereof.

In another embodiment, the anode is operating under plating conditionsbased on the temperature, voltage, charging-rate or combination thereof.

In yet another embodiment, the gate electrode is ionically conductivealong the thickness dimension and is electrically conductiveperpendicular to the thickness dimension.

In still another embodiment, the gate electrode comprises anelectronically conducting material as freestanding form, or filmdeposited upon an insulating substrate with sufficient porosity andtortuosity, and connected to external circuit through a dedicated tab.

In a further embodiment, the gate electrode has porosity sufficient tomaximize the efficiency of the permeability to at least one mobilespecies.

In yet a further embodiment, the gate electrode has porosity havingsufficient tortuosity to minimize the probability that a non-uniformmorphological feature projecting through the gate electrode fails tomake electrical contact to the gate.

In an additional embodiment, the device further comprises a responsecircuit configured to recognize a condition of an electrical shortcircuit between the gate electrode and a selected one of the anodeelectrode and the cathode electrode; and a stripping circuit configuredto apply a stripping current to the anode electrode sufficient to stripa non-uniform morphological feature to eliminate the electrical shortcircuit, the response circuit and the stripping circuit configured tooperate cooperatively.

In one more embodiment, the response circuit and the stripping circuitconfigured to operate cooperatively.

In still a further embodiment, the stripping circuit is configured toprovide a stripping current in the range of 0.01% to 10% of the currentat the metal anode electrode and the cathode electrode when the deviceis operated in charge or in discharge.

In one embodiment, the gate electrode is configured to operate withnet-neutral current flow with respect to the current at the metal anodeelectrode and the cathode electrode when the device is operated incharge or in discharge.

In another embodiment, the stripping current is applied between anodeand cathode.

In yet another embodiment, the device further comprises a cell chargingcircuit.

In still another embodiment, the cell charging circuit is configured toswitch from charge to discharge in the event that a non-uniformmorphological feature creates a low-impedance pathway between the gateelectrode and either of the cathode electrode and the anode electrode.

In a further embodiment, the discharge event has a current and durationcontrolled based upon the voltage sensed at the gate electrode.

In yet a further embodiment, the device comprises multiple gateelectrodes

According to another aspect, the invention relates to a multi-electrodeelectrochemical cell having more than two substantially parallelelectrodes in which at least one interior electrode comprises anionically permeable current-collector.

According to yet another aspect, the invention relates to anelectrochemical cell having a cathode electrode having a cathodeelectrical terminal, the cathode electrode in communication with aelectrolyte and an anode electrode having a anode electrical terminal,the anode electrode in communication with the electrolyte wherein theimprovement comprises at least one gate electrode having a gateelectrode electrical terminal, the gate electrode in communication withthe electrolyte and permeable to at least one mobile species which isredox-active at at least one of the anode and the cathode, the gateelectrode situated between the cathode electrode and the anodeelectrode.

According to still another aspect, the invention relates to anelectrochemical cell, comprising a cathode electrode having a cathodeelectrical terminal, the cathode electrode in communication with anelectrolyte; an anode electrode having a anode electrical terminal, theanode electrode in communication with the electrolyte; and a structurehaving a third electrical terminal, the structure in communication withthe electrolyte and permeable to at least one mobile species which isredox-active at at least one of the anode and the cathode, the structureconfigured to recognize the presence of an electrically conductivenon-uniform morphological feature that grows from either the cathodeelectrode and the anode electrode such that the non-uniformmorphological feature if permitted to grow without control would providean electrical short circuit between the cathode electrode and the anodeelectrode, and configured to receive a current at the third electricalterminal sufficient to strip a non-uniform morphological feature that iselectrically connected to either of the cathode electrode and the anodeelectrode.

According to a further aspect, the invention relates to anelectrochemical cell having a cathode electrode having a cathodeelectrical terminal, the cathode electrode in communication with anelectrolyte and an anode electrode having a anode electrical terminal,the anode electrode in communication with the electrolyte; wherein theimprovement comprises a structure having a third electrical terminal,the structure in communication with the electrolyte and permeable to atleast one mobile species which is redox-active at at least one of theanode and the cathode, the structure configured to recognize thepresence of an electrically conductive non-uniform morphological featurethat grows from either the cathode electrode and the anode electrodesuch that the non-uniform morphological feature if permitted to growwithout control would provide an electrical short circuit between thecathode electrode and the anode electrode, and configured to receive acurrent at the third electrical terminal sufficient to strip anon-uniform morphological feature that is electrically connected toeither of the cathode electrode and the anode electrode.

According to another aspect, the invention relates to an electrochemicalcell, comprising: a cathode electrode having an electrical terminal, thecathode electrode having a cathode shape, a cathode length, a cathodewidth and a cathode thickness, the cathode electrode in communicationwith an electrolyte; an anode electrode having an electrical terminal,the anode electrode having an anode shape, an anode length, an anodewidth and an anode thickness, the anode electrode in communication withthe electrolyte; at least one gate electrode having a gate electrodeelectrical terminal, the gate electrode in communication with theelectrolyte and permeable to at least one mobile species which isredox-active at least one of the anode and the cathode, the gateelectrode situated between the cathode electrode and the anodeelectrode; and a control circuit in electrical communication with atleast one of the cathode electrode and the anode electrode and inelectrical communication with the electrolyte, the control circuitconfigured to recognize and response the presence of an electricallyconductive non-uniform morphological feature that grows from either thecathode electrode and the anode electrode such that the non-uniformmorphological feature if permitted to grow without control would providean electrical short circuit between the cathode electrode and the anodeelectrode, and configured to provide a current to the gate electrodeelectrical terminal sufficient to strip a non-uniform morphologicalfeature that is electrically connected to either of the cathodeelectrode and the anode electrode.

In one embodiment, the control circuit is configured to apply anelectrical signal that limits the growth of the non-uniformmorphological feature so as to prevent an electrical short circuitbetween the cathode electrode and the anode electrode.

In another embodiment, the control circuit is configured to apply anelectrical signal that reverses the growth of the non-uniformmorphological feature.

In yet another embodiment, the control circuit is configured to limitthe growth of the non-uniform morphological feature so as to prevent achange in at least one of the cathode shape, the cathode length, thecathode width and the cathode thickness.

In still another embodiment, the control circuit is configured to limitthe growth of the non-uniform morphological feature so as to prevent achange in at least one of the anode shape, the anode length, the anodewidth and the anode thickness.

According to another aspect, the invention relates to a method ofoperating an electrochemical cell having an anode, a cathode, a gateelectrode, an electrolyte and a control circuit in electricalcommunication with at least one of the cathode electrode and the anodeelectrode and in electrical communication with gate electrode,comprising the steps of: measuring a selected one of a current and avoltage between at least two respective pairs of the cathode electrode,the anode electrode and the gate electrode to derive a value;determining an operating state of the electrochemical cell from thevalue; and if the operating state of the electrochemical cell is normal,waiting for a predefined length of time, and then repeating themeasuring step, and if the operating state of the electrochemical cellindicates that a short circuit is expected to occur, applying anelectrical signal configured to dissolve a growing non-uniformmorphological feature, and then repeating the measuring step.

In yet a further embodiment, the stripping circuit and the operatingconditions of the cell are configured to provide a voltage at the anodein the range of 0 V to 1.2V with respect to the metal-plating potentialof the redox-active species of the cell. In some embodiments, thevoltage in the range of 0V to 1.2V of the metal-plating potential is avoltage of 0.1V, 0.2V, 0.3V, 0.4V, 0.5V, 0.6V, 0.7V, 0.8V, 0.9V, 1.0V or1.1V from the metal-plating potential.

In a further embodiment, the device further comprises a response circuitconfigured to recognize a condition in which the gate electrode can nolonger be maintained at its target potential; and a charging circuitconfigured to trigger a discharge current between the cathode electrodeand the anode electrode when such a condition is sensed. Following aprescribed discharging event to strip the short, charging may resume.The discharge event triggered when such a condition is recognized may beoptimized for both rate and duration depending on the cell performanceand history and on the voltage measured at the gate electrode duringdischarge.

In yet another embodiment the device may further comprise a plurality ofgate electrodes configured to respond to the progressive growth ofnon-uniform morphological features across the cell. In such anembodiment, the plurality of gate electrodes may have a plurality ofexternal gate electrode terminals or alternatively may be connected to asingle external gate electrode terminal.

In still another embodiment, the gate electrode may be configured so asto protect against non-uniform morphological features only in specificregions of the cell. In some embodiments, the regions are the tabs orthe electrode perimeter regions.

According to one aspect, the invention features an electrochemical cellhaving one or more gate electrodes (that is, a third or subsequentelectrode) situated between a cathode and anode. The present disclosureaddresses the previously described fundamental problems through theaddition of one or more added “control” or “gate” electrodes interposedbetween the two working electrodes. The electrode is referred to as a“gate” because of its close analogy with the gate electrode in afield-effect transistor. This gate electrode allows control of theplating geometry of any metal or compound that would deposit near themetal plating potential by (a) setting a target cell chemical potentialunder a defined cell geometry (b) forcing stripping of depositedmaterial from the gate through application of appropriate potential and(c) detecting the point where the gate can no longer be maintained atits target potential. This not only enables enhanced operation ofmetal-electrode or other cells, it also enables faster cycling in anycell whose potential lies close to the metal plating potential, andenables a range of novel cell designs in particular multi-electrolytecells.

In another aspect, the gate electrode is both electrolytically andelectrically conductive. In some embodiments, the electrolyticconductivity is achieved by making the gate electrode porous.

In another aspect, the gate electrode provides a porous mechanicalbarrier between the anode and cathode having a characteristic porositysufficiently small so as ensure a high probability of contacting anon-uniform morphological feature extending from the anode towards thecathode before the non-uniform morphological feature creates ashort-circuit between the working (node and cathode) electrodes.

In another aspect, the gate electrode is configured to be substantiallygeometrically parallel to at least one of the anode or cathode. Inanother aspect, the gate electrode is in communication with a circuit todetect deviations from the target potential with nearly 100% efficacy.In another aspect, a current may be applied to the gate electrode tostrip non-uniform morphological features that have shorted to the gateelectrode and recondition a cell prior to a catastrophic short-circuitbetween the working electrodes.

In another aspect, a monitoring circuit detects incipient faults thatwould progress to cell short-circuit. In another aspect, areconditioning circuit functions to strip down non-uniform morphologicalfeatures, thereby reconditioning the cell for continued safe use.

In one embodiment, the electrochemical cell is a secondary battery andthe working electrodes include at least one anode and at least onecathode.

The foregoing and other objects, aspects, features, and advantages ofthe invention will become more apparent from the following descriptionand from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.

FIG. 1 (Prior Art) illustrates a basic electrochemical cell.

FIG. 2 (Prior Art) illustrates a battery constructed from at least twoelectrochemical cells.

FIG. 3 (Prior Art) illustrates problems affecting cells, namelynon-uniform morphological feature formation and the accretion ofisolated metal complexes.

FIG. 4 (Prior Art) illustrates a battery with an inactive externalelectrode according to Roh.

FIG. 5 (Prior Art) illustrates the internal construction of the batteryof FIG. 4.

FIG. 6 (Prior Art) illustrates a liquid electrolyte cell with a thirdelectrode according to Meissner.

FIG. 7 (Prior Art) illustrates an air-electrolyte cell having a thirdelectrode according to Zhong.

FIG. 8 (Prior Art) illustrates a cell according to Slezak having a thirdelectrode to increase surface area.

FIG. 9 (Prior Art) illustrates cells having an externally exposedextension of an electrode according to Morris.

FIG. 10 (Prior Art) illustrates the construction of a battery using thecell of FIG. 9.

FIG. 11 (Prior Art) illustrates a three electrode cell where the thirdelectrode is a non-participating metallic reservoir configured toreplenish metal ions depleted by the mechanisms in FIG. 3.

FIG. 12 (Prior Art) illustrates a cell with an intermittently connectedLithium reservoir electrode according to Christensen.

FIG. 13 (Prior Art) illustrates a cell where one of the electrodes isextended or electrically connected to a third electrode to providenon-interfering access to the cell for temperature or othermeasurements.

FIG. 14 (Prior Art) illustrates a battery according to Kaneta employingelectrodes for sensing.

FIG. 15A (Prior Art) illustrates a cell according to Ramasubramanianwith a three dimensional configuration of anode and cathode, with theaddition of a third Auxiliary electrode that provides a reservoir forLithium.

FIG. 15B (Prior Art) illustrates the cell of FIG. 15A and an associatedsensing circuit.

FIG. 16A (Prior Art) is a copy of FIG. 8 from Noguchi (WO 2011/070712A1) showing the electrically conductive layer (4) that is not used aftershipment of the lithium ion secondary battery.

FIG. 16B (Prior Art) is a copy of the prior art FIG. 1a and FIG. 1b ofCui (PCT/US2014/036631).

FIG. 17 illustrates a coated metallic electrode surface.

FIG. 18 illustrates the failure of the coating the electrode of FIG. 17resulting in plating of the coating.

FIG. 19 illustrates a cell according to the present disclosure, whichincorporates a gate electrode.

FIG. 20 illustrates a configuration of a gate electrode composed from alaminate of a highly conductive coarse mesh and a conductive fine mesh.

FIG. 21 shows a commercial separator treated with a thin metal film.

FIG. 22 shows a thin metal coated separator combined with a thick metalgrid.

FIG. 23 illustrates an embodiment of a cell having an anode electrode, acathode electrode, and a gate electrode which incorporates a gatestructure with separators.

FIG. 24 illustrates a cell charge, discharge and stripping cycle.

FIG. 25A illustrates a method of detecting an incipient cell short, andresponding to such detection with a reconditioning step, and theresistance requirements for the proposed gate electrode versus theaffected working electrode.

FIG. 25B illustrates the operating voltages for the gate relative to theworking electrodes.

FIG. 26 is a flow chart illustrating the operating method for a cellprotected according to the present disclosure.

FIG. 27 is a flow chart illustrating an alternative operating method fora cell protected according to the present disclosure.

FIG. 28 is a schematic of a prior art control circuit that can be usedto operate a multi-electrode electrochemical cell according to thepresent disclosure.

FIG. 29A is a graph of the cell voltage (i.e., the voltage measuredbetween the positive and negative cell terminals) as a function of timefor a rechargeable Li metal secondary cell wherein the N/P capacityratio ≦1.

FIG. 29B is a graph that depicts the gate voltage (i.e., the voltagemeasured between the gate and negative cell terminal in this case) as afunction of time for a rechargeable Li metal secondary cell wherein theN/P capacity ratio ≦1.

FIG. 30 depicts the cathode energy density as a function of cycle numberfor gated rechargeable Li metal secondary cell wherein the N/P capacityratio ≦1.

FIG. 31 depicts the average charge and discharge voltage as a functionof cycle number for gated rechargeable Li metal secondary cell whereinthe N/P capacity ratio ≦1.

FIG. 32 depicts a segment of the cell voltage and gate voltage as afunction of cycle number for gated rechargeable Li metal secondary cellwherein the N/P capacity ratio ≦1 under active control.

FIG. 33 is an image of a test apparatus for operating a cell accordingto the present disclosure, which incorporates a gate electrode.

DETAILED DESCRIPTION Discussion of Problems with the Prior Art

FIG. 1 (Prior Art) shows a “conventional,” two-electrode secondaryelectrochemical cell 110, which includes a cathode 120, an electrolyte130, and an anode 140. The cell produces a characteristic voltage basedon the difference between the electrode potentials of the cathode 120and the anode 140. The electrolyte 130 may have mechanical propertiesenabling it to function as a separator between the electrodes. Theelectrodes may be metallic or a combination of active and inertmaterials. During charging, electrons are generated at the cathode 120,and are consumed at the anode 140. The electrons are transferred via anexternal circuit. During charging of a typical metal-ion based cell,there is an accretion of metal-ions at the anode 140. In a cell with ametallic electrode, charging results in plating of the anode 140. In acell with a non-metallic electrode, charging ideally results inintercalation of metal ions into the electrode, but if the intercalationpotential is too close to the metal plating potential, metal may alsoplate in this instance.

FIG. 2 (Prior Art) shows that such cells 110 are typically stackedtogether to form a battery 210 that provides a multiple of thecharacteristic voltage. Some electrochemical systems are well suited tothin planar electrodes and electrolytes, and lend themselves to theconstruction of compact planar stacks of cells to produce higher voltagebatteries in a small volume.

FIG. 3 (Prior Art) shows two serious problems that occur in secondarycells. The cell 310 contains the conventional cathode 320, electrolyte330, and anode 340. During the charge/discharge cycle, it occurs thatthe geometry of the working electrodes can evolve to the detriment ofthe cell.

In particular, non-uniform morphological features 350, of metal may beformed on the surface of the anode 340. If the non-uniform morphologicalfeature 350 grows sufficiently long to reach the cathode 320, the cellwill short-circuit. This short-circuit disables the cell, and can alsolead to a destructive exothermic reaction with catastrophic results.Another problem with conventional cells is that side reactions of theelectrolyte 330 can lead to the formation of excess electrolyteinterphase 360, called “mossy” deposits, within the interior volume ofthe cell, which creates isolated deposits of metal that is subsequentlyunable to participate in the operation of the cell. To some extent, theproblems of non-uniform morphological features and mossy deposits can bemanaged by limiting the conditions of charge and discharge, but thislimits the capacity and utility of the cell. It has also been suggestedthat material improvements to electrode materials could minimize theformation of non-uniform morphological features, but such improvementswould still leave a cell vulnerable to eventual failure with no means ofdetection prior to a catastrophic event, and no way to repair the cell.Because no non-interfering way to detect incipient failures duringnormal operations is available for such cells, the only conclusive wayto determine a cell failed due to dendritic shorting is the destructivedisassembly of the cell during an autopsy.

FIG. 4 (Prior Art) illustrates a battery with an external electrode madeof an inactive material according to Roh. Here, the one of theelectrodes of a cell that is extended out of the active plane of thecell is used to provide interconnection points for composing cells intoa battery assembly. The extended electrodes do not participate in theenergy extraction or control of the cell. Inactive electrodes cannot beused to address the problems associated with non-uniform morphologicalfeatures or mossy deposits.

FIG. 5 (Prior Art) illustrates the internal construction of the batteryof FIG. 4. A different material 55 from the active electrodes is used asa current collector and extended to provide cell interconnection points.While characterized by Roh as a third electrode, the assembly 50 havingan active material 52, a collector 51 and an inactive material 55 areelectrically equivalent to a single electrode. While providingmechanical advantages, this assembly cannot be used to address problemssuch as non-uniform morphological features or mossy deposits.

FIG. 6 (Prior Art) shows a liquid electrolyte cell, according toMeissner, modified by the addition of an auxiliary electrode 16. As withChristensen, the auxiliary electrode disposed within the electrolyte 22provides a reservoir for lithium for adding metal ions to the cell. Theauxiliary electrode 16 is only intermittently in contact with the cell'sliquid electrolyte, and does not participate in the normal charge anddischarge cycle. The cell must be reoriented to control the auxiliaryelectrode's contact with electrolyte. The auxiliary electrode mayprovide some sensing function. The auxiliary electrode has an areasubstantially smaller than either of the working electrodes, and doesnot create a barrier between the anode and cathode. Because of theseproperties, the auxiliary electrode in Meissner cannot be used toaddress problems such non-uniform morphological features or mossydeposits.

FIG. 7 (Prior Art) shows, as an example of another cell type has an airelectrode 102 and a metal electrode 106. In addition, it includes acounter (third) electrode 104, a metal air tricell 100 according toZhong. A third electrode has also been extensively investigated in thisso-called “tricell” configuration for an air cathode. In these cellsthere are competing requirements for the catalyst during theoxygen-evolving and oxygen-consuming phases (charge and discharge). Thetricell configuration addresses these different requirements by usingtwo cathodes comprising different catalysts; for example a metalcatalyst and an oxide catalyst. Since the goal of these schemes is tocharge from one electrode and discharge to the other, the net current onone of the electrodes is always zero. Thus the counter (third) electrode104 serves no sensing or reconditioning function, and thus cannot beused to solve problems such as non-uniform morphological features ormossy deposits even if this type of electrode was added to a non-airtype cell.

FIG. 8 (Prior Art) illustrates a cell according to Slezak having a thirdelectrode to increase surface area. The electrode has a folded shape andis directly connected to an internal electrode and is thus always at thesame potential as the internal electrode. In this sense, the thirdelectrode is not independent. The increased surface area improves theperformance of the cell, but does not provide any active control ormeasurement capability, and thus cannot be used to address problems suchnon-uniform morphological features or mossy deposits.

FIG. 9 (Prior Art) illustrates cells having an externally exposedextension of an electrode according to Morris. Similarly to Roh, theextended electrode serves to provide external interconnects. In Morris,these electrodes do not cover the entire plane of the cell, and thuscannot provide a uniform active surface. The extended electrode cannotbe used to address problems such as such non-uniform morphologicalfeatures or mossy deposits. However, the extended electrodes allow acompact assembly of cells into a battery.

FIG. 10 (Prior Art) illustrates the construction of a battery using thecell of FIG. 9. The extended electrodes are used as current collectorsand connect the individual cells with no increase the height of the cellstack. While the scheme of Morris provides mechanical advantages, theextended electrodes are electrically equivalent to the workingelectrodes and cannot be used to address problems such as suchnon-uniform morphological features or mossy deposits.

FIG. 11 (Prior Art) shows a cell 1110, according to Christensen,incorporating a third electrode that provides a reservoir 1150 of metalin communication with an electrolyte 1130 to replace metal lost duringcharge and recharge cycle, providing the ability to “top up” the activeLi in a cell. During normal operation the reservoir remains electricallydisconnected from the operation of the cell. The reservoir is activatedwhen degradation in cell performance has been detected and used as asource of metal to rebalance the cell's operation. Because the reservoiris designed not to interfere in normal cell operation, it is disposedout of the plane formed between the working electrodes (anode 1140 andcathode 1120), off to the side of the cell. The reservoir electrode isplaced outside and adjacent to the primary conduction pathways of thecell but in contact with the electrolyte. The reservoir electrode is notcoplanar with the remainder of the stack, and a bias is onlyintermittently provided to the reservoir electrode with respect to oneor both of the working electrodes in order to replenish Li lost duringcycling of Li-ion cells (as opposed to Li metal). While this approachcan address the degradation in performance is identified by either“capacity fade” or “power fade” due to the effective loss of workingions, Christensen's reservoir cannot be used to address problems suchnon-uniform morphological features or mossy deposits for severalreasons. First, the reservoir doesn't participate in the normal chargeand discharge cycle, and is thus not able to monitor the state ofnon-uniform morphological features. Second, the reservoir is not locatedbetween the working electrodes forming a complete separator, so the cellcould not be fully protected by any mechanical function the reservoirprovided. Christensen also provides for monitoring by using thereservoir electrode as a reference or auxiliary electrode. During mostof the cycle life of the cell, the reservoir electrode sits atopen-circuit or operates as a sensing/auxiliary/reference electrodeoperating at minimal current. Only during charging or discharging is thereservoir electrode biased relative the anode (charging) or cathode(discharging) so as to introduce additional Li into the cycle. In orderto function, the reservoir electrodes must deliver Li to the workingelectrodes, i.e. the average current between the reservoir electrode andthe operating cell must be positive; likewise, the voltage during theoperation of the reservoir electrode must also be positive.

FIG. 12 (Prior Art) illustrates the cell of FIG. 11, and the controlcircuits which enable with the Lithium reservoir electrode to beintermittently connected when replenishment or reduction in the amountof Lithium cation is required. The Lithium reservoir electrode is incontact with the cell's electrolyte, but unless one of the switches 613or 614 are closed from their normally open state, the Lithium reservoirelectrode remains electrically isolated. When one of the switches isclosed, and the correct voltage applied, Lithium can be added or removedfrom the active portion of the cell. This Lithium management functiondoes not address problems such as such non-uniform morphologicalfeatures or mossy deposits.

FIG. 13 (Prior Art) shows a cell 1310 according to Kaneta, where eitherthe anode 1340 or the cathode 1320 is attached to an additional mass ofelectrode material 1350 that might be considered a third electrode. Inthis cell, the additional electrode material is mechanically anddirectly electrically connected to one of the working electrodes butmechanically disposed external the plane of the working electrodes. Theadditional electrode is not necessarily in direct contact with theelectrolyte 1330. Thus, the additional electrode material is readilyaccessible as a measurement point such as, for example, for temperature,but is always operating at the same potential as the working electrodeto which it is electrically connected. Therefore, the additionalelectrode material cannot be used for any purpose that does not assume acontinuous connection to a working electrode. Because it is directlyelectrically connected to one or other working electrode, the additionalelectrode is not electrically distinct from the working electrodes, andcannot be used address problems such as such non-uniform morphologicalfeatures or mossy deposits.

FIG. 14 (Prior Art) illustrates a battery according to Kaneta in FIG. 13employing electrodes for sensing which extend directly out of the planeof each cell. The arrangement in Kaneta allows for sensing without thenecessity of inserting sensing probes or adding thickness to the stack.However, the sensing electrodes do not participate in the energy storageor release chemistry of the battery, and cannot be used address problemssuch as such non-uniform morphological features or mossy deposits.

FIG. 15A (Prior Art) shows a three-dimensional cell 1510 according toRamasubramanian. The cell has working electrodes anode 1520 and cathode1530 having a non-planar geometry that provides a large surface area toincrease the capacity of the cell. The auxiliary electrode 1550 of thiscell is arranged to be in the relatively uniform proximity to at leastone of the working electrodes, but is not located between the workingelectrodes, but is in contact with the electrolyte (not illustrated).The auxiliary electrode is able to carry significant currents, so as tosupport more uniform charging of the cell. Because of the threedimensional nature of the electrodes, the distance between the auxiliaryelectrode and the relevant working electrode varies substantially,limiting the utility of the auxiliary electrode only to functionsunconcerned with local geometric evolution of the relevant workingelectrode. The auxiliary electrode is not located between workingelectrodes. Therefore, the auxiliary electrode cannot be used to managelocal phenomena that occur between the working electrodes, and cannot beused to manage phenomenon related to non-uniform morphological features.Rather, Ramasubramanian is directed to optimizing charging and alsotoward using the auxiliary electrode as a lithium reservoir. The threedimensional cell of Ramasubramanian cannot be used to address problemssuch non-uniform morphological features or mossy deposits.

FIG. 15B (Prior Art) illustrates the cell of FIG. 15A and an associatedsensing circuit. The sensing and control unit 27 is used to maintain adesired potential of the auxiliary electrode 24 to improve theperformance of the cell, but not to address such as non-uniformmorphological features or mossy deposits.

Noguchi Prior Art

The Noguchi patent appears to disclose (as recited in a translationprovided by the Korean Intellectual Property Office) that theelectrically conductive layer (4) is made by forming a Cu layer of about0.5 μm thickness on one side of a polypropylene sheet of 18 μm thicknessusing ion beam sputtering deposition, or in alternatives, RF ormagnetron sputtering. After mechanical assembly, electrolyte was addedto the secondary battery. It was then charged. After charging, theelectric potential difference between the electroconductive layer andthe cathode (16) and current can be measured.

The Noguchi patent is said to disclose (as recited in a translationprovided by the Korean Intellectual Property Office) that the effect ofthe invention is to detect with high sensitivity internal short-circuitsin lithium ion secondary batteries caused by foreign metal matter.

The electroconductive layer described is a passive device in that nopotential is applied during operation of the cell. In fact the purposeof the electroconductive layer is to aid in the detection ofmanufacturing defects prior to shipment of the cell. The documentspecifically addresses the issue of short circuits created by thepresence of metallic particle impurities that are introduced during themanufacturing process. Thus in actual operation of the cell (aftershipment), no bias is applied nor current sensed. Further, the inventionis described throughout as a means to detect internal short-circuits,detection being inherently passive and not affecting the deviceoperation except to drive decisions regarding rejection of defectivecells.

The Noguchi patent is said to disclose (as recited in a translationprovided by the Korean Intellectual Property Office) that “Moreover, theelectrically conductive layer (4) specially does not use after theshipment of the lithium ion secondary battery. Therefore the terminal(10) connected to the electroconductive layer is hidden to the memberafter the inspection before the shipment or the terminal (10) and thelead line connected to the electroconductive layer can be removed.”

The Noguchi patent does not appear to describe how one might use theelectrically conductive layer (4) to remove dendrites from a working Lisecondary battery, or from any secondary battery. Rather, the Noguchipatent appears only to teach how one may detect manufactured secondarybattery devices that are shorted and therefore are defective.

FIG. 16A (Prior Art) is a copy of FIG. 8 from Noguchi (WO 2011/070712A1) showing the electrically conductive layer (4) that is not used aftershipment of the lithium ion secondary battery.

Cui Prior Art

FIG. 16B (Prior Art) is a copy of the prior art FIG. 1a and FIG. 1b ofCui (PCT/US2014/036631).

In particular, Cui shows in FIG. 1a and FIG. 1b thereof the use ofvoltmeters to measure voltages between various electrodes in a secondaryLi battery. As is well known in the electrical measurement arts, avoltmeter needs to have a high input impedance in order to avoid loadingthe circuit that is being measured. Meters with electronic amplifiers(all digital multimeters and some analog meters) have a fixed inputimpedance that is high enough not to disturb most circuits. This isoften either one or ten Megaohms: the standardization of the inputresistance allows the use of external high-resistance probes which forma voltage divider with the input resistance to extend voltage range upto tens of thousands of volts. High-end multimeters generally provide aninput impedance greater than 10 Gigaohms for ranges less than or equalto 10 V. Some high-end multimeters provide greater than 10 Gigaohms ofimpedance to ranges greater than 10 V. Given that such meters operatefrom power supplies having operating voltages below 10 volts, and oftenlower than 5 volts, the current that would flow in sensing a shortcircuit (e.g., measuring a voltage of zero volts) would be less than10⁻⁷ amperes with a meter having 10 Megaohm input impedance and lessthan 10⁻¹⁰ amperes with a meter having 10 Gigaohm input impedance,either of which is insufficient to have any effect on a dendrite in asecondary battery.

The device described in Cui is a passive device. The device is notconfigured to allow bias to be applied to the third electrode duringoperation of the cell. Instead of a current or voltage source applied tothis electrode, the device contains a voltage-sensing device, such as avoltmeter. The operation of the voltage-sensing is inherently passive;the impedance of voltmeters is high so as to minimize interference ofthe sensing device with the operation of the circuit being sensed, andthe voltage of all of the electrodes will remain at the same potentialthat they would be at in the absence of the sensing device. Because itis passive, the Cui invention like the Noguchi device may serve toreject defective cells but does not provide any improvement to theoperation of the cell.

In summary, the use of more than two electrodes in electrochemical cellsfor a variety of uses is well known, but none of these prior uses canstrip non-uniform morphological features or actively manage the healthof the working electrodes.

Roumi Disclosures

Roumi, U.S. Ser. No. 14/546,953 filed Nov. 18, 2014 and published Jun.18, 2015 as U.S. Patent Application Publication No. 2015/0171398 A1, andRoumi, U.S. Ser. No. 14/546,472 filed Nov. 18, 2014 and published Jun.25, 2015 as U.S. Patent Application Publication No. 2015/018000 A1, bothclaim the priority and benefit of U.S. provisional patent applicationSer. No. 61/905,678, filed Nov. 18, 2013, U.S. provisional patentapplication Ser. No. 61/938,794, filed Feb. 12, 2014, and U.S.provisional patent application Ser. No. 61/985,204, filed Apr. 28, 2014(collectively “the earliest three Roumi provisionals”), prior to thefiling date of U.S. provisional patent application Ser. No. 62/020,337,filed Jul. 2, 2014, from which the present application derives priorityand benefit. The two Roumi applications also claim the priority andbenefit U.S. provisional patent application Ser. No. 62/024,104, filedJul. 14, 2014.

Under the present first to file legal regime, none of the additionalmaterial disclosed in either U.S. patent application Ser. No. 14/546,953or U.S. patent application Ser. No. 14/546,472 that was not present inany of U.S. provisional patent application Ser. Nos. 61/905,678,61/938,794, and 61/985,204 represents prior art to U.S. provisionalpatent application Ser. No. 62/020,337, filed Jul. 2, 2014, the priorityand benefit of which application is claimed herein.

In the provisional patent applications mentioned above, Roumi does notdescribe or show any apparatus for applying a bias to a third electrodeduring operation of the cell.

U.S. provisional patent application Ser. No. 61/905,678, filed Nov. 18,2013, describes that short circuits are sensed and potentially mitigatedthrough the use of physical obstruction or thermal diffusion byemploying mechanically robust composite separators or elastomericcurrent collectors that combine layers of conductive and insulativematerials. However it does not provide any description of a cellcomprising a separate third electrode, or a cell wherein three separateelectrical signals between pairs of electrodes (i.e., between thepositive and negative electrodes, between the positive and gateelectrodes, or between the negative and gate electrodes) can berecognized, and modified or controlled. The application states that “itis important to note that the second active material does not need to bephysically connected to the said current collector directly; and itdoesn't need to be in complete physical contact with the said firstactive material at all times.” It does not describe control of a cellutilizing more than two electrodes, within the cell, or at the circuitboard, or any combination thereof. The conducting/insulating layers aresimply a separator.

U.S. provisional patent application Ser. No. 61/938,794, filed Feb. 12,2014, describes a conductive layer is “introduced into the space betweenopposite electrodes” as a method to control the surface of electroplatedmaterial. The inventor indicates that “the conductive layer may or maynot be electronically connected to the opposing electrode. Further, theconductive layer may or may not be physically connected to the opposingelectrode” hence the conductive layer is either isolated within thecell, or an additional conductive layer upon either the positive ornegative electrode. This definition of the conductive layer is inclusiveof the types of conducting materials that inadvertently find way into afinite number of defective cells produced during the manufacturingprocess. That application does not make any description of a cellcomprising a separate third electrode, or a cell wherein three separateelectrical signals between pairs of electrodes (i.e., between thepositive and negative electrodes, between the positive and gateelectrodes, or between the negative and gate electrodes) can berecognized, and modified or controlled. U.S. provisional patentapplication Ser. No. 61/985,204, filed Apr. 28, 2014 describes thatshort circuits are sensed and potentially mitigated through the use ofphysical obstruction or thermal diffusion in “an electrochemical cell .. . consisting of an anode, a cathode, an electrolyte, one or moreseparator layer(s) and an electronically conductive layer.” Theinventors claim “[t]he electronically conductive layer may have noelectronic connections with one of the electrodes or may have noelectronic connections with any of the electrodes.” The application doesnot provide any description of a cell comprising a separate thirdelectrode, or a cell wherein three separate electrical signals betweenpairs of electrodes (i.e., between the positive and negative electrodes,between the positive and gate electrodes, or between the negative andgate electrodes) can be recognized, and modified or controlled. In oneaspect the conducting/insulating layers are simply a separator asdefined by U.S. provisional patent application Ser. No. 61/905,678,filed Nov. 18, 2013, while in another aspect the definition of theconductive layer is inclusive of the types of conducting materials thatinadvertently find way into a finite number of defective cells producedduring the manufacturing process as defined by U.S. provisional patentapplication Ser. No. 61/938,794, filed Feb. 12, 2014.

U.S. provisional patent application Ser. No. 62/024,104, filed Jul. 14,2014 presents the definition of the “low resistance conductive layer”specifically to ionic conductivity, rather than electronic conductivityas described in the present invention. For example U.S. provisionalpatent application Ser. No. 62/024,104 provides a description of “anelectrochemical cell the separator consists of a separator-bag for theanode and the separator itself can consist of more than one layer; forexample the separator-bag can be made of a strong porous or perforatedlayer (such as mylar film with 40% holes, hole sizes can be fromnanometers to millimeters) covering the entire anode surface and a lowresistant layer (such as nonwoven polyolefins) on the outer side awayfrom the anode, facing the rest of the cell and the cathode.” Thatapplication does not provide any description of a cell comprising aseparate third electrode, or a cell wherein three separate electricalsignals between pairs of electrodes (i.e., between the positive andnegative electrodes, between the positive and gate electrodes, orbetween the negative and gate electrodes) can be recognized, andmodified or controlled.

Roumi, U.S. patent application Ser. No. 14/546,953 filed Nov. 18, 2014and published as U.S. Patent Application Publication No. 2015/0171398 A1on Jun. 18, 2015, is said to disclose electrochemical cells including acomposite separator capable of changing the performance of the cell bya) changing the internal electric field of the cell, b) activating lostactive material, c) providing an auxiliary current collector for anelectrode and/or d) limiting or preventing hot spots and/or thermalrunaway upon formation of an electronic short in the system. Anexemplary composite separator includes at least one electronicallyconducting layer and at least one electronically insulating layer.Another exemplary composite separator includes an electronicallyconducting layer and a solid ionic conductor. Also disclosed are methodsfor detecting and managing the onset of a short in an electrochemicalcell and for charging an electrochemical cell.

U.S. patent application Ser. No. 14/546,953 describes a cell comprisinga third electrode, or a cell wherein three separate electrical signalscan be sensed despite the lack of such disclosure in any of the parentapplications that it claims priority. It is notable that describing the“conductive layer” more like a third electrode and less like thecomposite separator previously described, this Roumi application sharessimilar description to Cui, et al., U.S. Patent Application PublicationNo. 2014/0329120 A1, published Nov. 6, 2014 (simultaneously with Cui, etal., WO 2014/179725 A1), which is said to disclose a battery thatincludes: 1) an anode; 2) a cathode; 3) a separator disposed between theanode and the cathode, wherein the separator includes at least onefunctional layer; and 4) a sensor connected to the at least onefunctional layer to monitor an internal state of the battery.

Therefore, the new material disclosed only in U.S. patent applicationSer. No. 14/546,953 and not in any of the earliest three Roumiprovisionals is not prior art to this application. However, forcompleteness, it is differentiated from the disclosure enclosed hereinfor the same reasons as Patent Application Publication No. 2014/0329120A1.

Roumi, U.S. Patent Application Publication No. 2015/018000 A1, publishedJun. 25, 2015, is said to disclose electrochemical cells including aseparator enclosure which encloses at least a portion of a positive ornegative electrode. In an embodiment, the separator generates a contactforce or pressure on at least a portion of the electrode which canimprove the performance of the cell. The disclosure also providesmethods for charging an electrochemical cell.

U.S. patent application Ser. No. 14/546,472 filed Nov. 18, 2014 andpublished Jun. 25, 2015 as U.S. Patent Application Publication No.2015/018000 A1 also describes the use of an active third electrode to“modify the performance of the cell by applying an external voltage”.The Application discloses two such uses. First, [para 0060] the“application of voltage . . . can be used to “clean up” the cell”.Examples are provided of specific examples of impurities and by-productsin certain chemistries including which may be eliminated by theapplication of a voltage to this electrode “e.g. every 50 cycles”.Further [para 0076], “the electronically conductive layer provides asource of active ions” which may be used “to compensate the ion loss orto make Li-ion cells with non-lithiated electrode”. This appears similarto the Christensen Li “reservoir” and is differentiated from the presentinvention for the same reasons.

Therefore, the new material disclosed only in U.S. patent applicationSer. No. 14/546,472 and not in any of the earliest three Roumiprovisionals is not prior art to this application. However, forcompleteness, it is differentiated from the disclosure enclosed hereinfor the same reasons as Patent Application Publication No. 2014/0329120A1.

Benefits Provided by the Present Invention

A technology that would enable the use of composite or metallic workingelectrodes would enable the capacity of batteries to increase. Atechnology that also allowed the use of metallic electrodes wouldprovide the potential for performance improvements in many“next-generation” chemistries including without limitation not onlyMagnesium, but also Li-metal, Li-air, and Zn-air. In addition, atechnology that would mitigate failure-modes, due to a change in themorphology of one or both electrodes that can lead to a short-circuitelectrical condition, would allow for greatly enhanced performance incells utilizing conventional intercalation host electrodes including,but not limited to graphite, or alloying, conversion, anddisproportionation reaction electrodes. Even better would be atechnology that allowed for batteries to be reconditioned from anincipient failure state, extending the life of a given battery. Thepresent application provides systems and methods that address all ofthese desirable improvements.

Description of the Multi-Electrode Electrochemical Cell

A cell constructed and operated according to the present disclosure canactively prevent the formation of non-uniform morphological features byactive control of the voltage or potential of a gate electrode. Further,the gate electrode can be used to provide a current to strip non-uniformmorphological features down so that the cell may be restored to normaloperation and the life of the cell can be extended. The current requiredto maintain the target voltage of the gate electrode also provides theability to monitor cell health, and thus to actively manage the chargingand discharging of the cell to optimize performance, capacity and tominimize the formation of non-uniform morphological features and “mossy”deposits.

FIG. 19 shows a cell 1910 according to the present disclosure. This cellincorporates a porous gate electrode 1940 in contact with theelectrolyte 1930, which is disposed between the cathode 1920 and theanode 1950. The gate electrode 1940, cathode 1920 and the anode 1950 areall arranged so that each is substantially parallel to one another onlocal scale. That is, the overall cell could contain complex curves, aslong as the layers were locally parallel enough that the cell performedsubstantially as though the entire cell was planar. The gate electrode1940 is located a distance from the anode 1950 such that a non-uniformmorphological feature growing from the anode 1950 has an extremely highprobability of contacting the gate electrode 1940. In one embodiment, innormal operation the gate electrode 1940 is set to be at a selectedpositive voltage relative to the anode 1950, for example by a controlcircuit. The voltage is selected such that it sets a local chemicalpotential which is sufficient to initiate stripping of plated metal, forexample plated metal derived from at least one mobile species which isredox-active at at least one of the anode 1950 and the cathode 1920. Thevoltage required to initiate such stripping (e.g., a predeterminedstripping potential) is well-established for a given electrochemicalsystem. During normal operation, the gate thus provides a “guaranteedmetal-free” zone where the local chemical potential of the cellprohibits the presence of metal. In the case that a non-uniformmorphological feature on the anode touches the gate electrode, the tipof the dendrite will be shorted to the gate potential. Since there isnow metal at its stripping potential, the non-uniform morphologicalfeature will be stripped. The gate is connected to a current-source inorder to accomplish this outcome, and during the brief period when thereis contact between the gate and a non-uniform morphological feature, thecurrent-source connected to the gate needs to supply a current ofsufficient magnitude to perform this stripping operation. At othertimes, the current-source only needs to supply a current of sufficientmagnitude to maintain the gate voltage at the metal-free potential.

In addition to maintaining a metal-free zone within the cell, the gateprovides an ongoing measure of the cell's propensity for shorting. Thecurrent required to maintain the gate voltage is a measure of the numberand size of incipient events which the gate is preventing. Bymaintaining the gate at a metal-free potential and measuring the currentrequired to maintain that potential, it is thus possible to assess thelikelihood of a shorting event occurring which will move the gate to theanode potential. If the gate shifts to the anode potential there is nolonger a guaranteed metal-free zone within the cell, and the cell is atrisk for shorting. Thus in some instances, at a point where a currentrequired to maintain the gate at target potential exceeds some targetthreshold, it may be desirable to stop the cell from further cycling andremove it from service. This threshold may be chosen based on the sizeof the cell, the impedance of the anode and gate, and the undesirabilityof a cell failure in a given application.

In still a further implementation of this invention, a stripping circuitmay be included which can be used in response to the changes in the gatecurrent. In the event that a morphological feature contacts the gateelectrode 1940, there will be an increase in the current required tohold the gate electrode 1940 at the stripping potential. This increasein the current may be observed, recognized and recorded. At this time, acontrol circuit may reverse the voltage applied to the gate electrode1940 and the anode 1950 for a suitable time period, stripping down thenon-uniform morphological feature. Thus the cell 1910 is protected froma fatal short circuit.

FIG. 20 shows an embodiment of the gate electrode 1940. To functionappropriately, the gate must allow for electrolytic conduction acrossits thickness and be an electrical conductor along its length.Electrolytic conduction is necessary because the gate electrode 1940 isdisposed between a cell's working electrodes and should be astransparent as possible in normal operation. One method for allowingelectrolytic conduction is to arrange the structure of the gate to befreely porous to whatever electrolyte is being used in the cell. Thegate electrode must be electrically conductive in its plane so that itmay be used to measure local voltage in idle mode, and be used todeliver current to the anode in stripping mode. The structure of thegate, while porous, needs to have a sufficiently fine pore structure sothat a non-uniform morphological feature passing through the structurehas a very high probability of making electrical contact. One way toprovide porosity and still not allow a non-uniform morphological featureto penetrate the gate electrode is to make the porous channels tortuousor nonlinear in geometrical extent as one passes from one side of thegate electrode to the other side. In a non-limiting example, these goalscan be achieved by laminating a highly conductive coarse mesh 2030,capable of delivering an appropriate stripping current, with aconductive fine mesh 2020 whose pores are too small for a non-uniformmorphological feature to pass though without contact. The laminated gatehas favorable mechanical and electrical properties, while providing thespatial fineness to ensure the gate can prevent incipient faults fromnon-uniform morphological feature growth. In particular as shown in FIG.24B, the gate resistance R_(gate) should be made smaller than theresistance of a non-uniform morphological feature R_(numf) so that thenon-uniform morphological feature can be stripped.

FIG. 21 shows a potential implementation of a gate electrode comprisinga commercial separator treated with a thin metal film. The commercialseparator is a polymer based layer that is electrically insulating andhas fine pores that allow electrolyte flow between the workingelectrodes. These pores are sufficiently small that it is highlyimprobable that a non-uniform morphological feature could pass throughthe mesh without making physical contact with the material. A widevariety of such materials are well known in the art and are used in thevast majority of commercial cells. The commercial separator is astarting point for the gate electrode, and can be added to the cellparallel to the working electrodes disposed between the workingelectrodes so as to completely separate the working electrodes. However,as supplied, the commercial separator material is not useful forprotecting the cell from the previously mentioned failure anddegradation modes, because the impedance of the separator is effectivelyinfinite, so that in the event that a non-uniform morphological featurecontacts such a gate, the local gate potential would move to the platingpotential and the non-uniform morphological feature would continue togrow. Therefore, a thin metallic plating is applied to the mesh. Afterthis treatment the separator mesh can be attached to a current-supplycircuit, and the impingement of a non-uniform morphological feature canbe prevented. Such a treated separator may be sufficient. However insome non-limiting embodiments, this metalized mesh has insufficientconductance to achieve the goals of the present disclosure because themesh is not conductive enough.

FIG. 22 shows an alternative embodiment, where a thin metal coatedseparator combined with a robust metal grid. The metal grid is highlyconductive and has sufficient current carrying capacity to stripundesired non-uniform morphological features off of a working electrode.In some non-limiting embodiments, the grid's filaments are too far apartto ensure that a non-uniform morphological feature would make contactwith the grid while passing through the grid. Consequently the gridalone may be insufficient to achieve the goals of the presentdisclosure. By laminating the metalized mesh of FIG. 21 with the thickmetal grid, a composite structure with excellent properties is created.

Whether made from a homogeneous or composite, as in the embodimentsdescribed above, any structure that is, for the given working conditionsof the cell, 1) ionically conductive, 2) has a pore size small enough toensure contact with a non-uniform morphological feature growing off of aworking electrode towards the center of the cell, 3) highly conductiveso that energy is not dissipated in the laminated structure and 4) hashigh current carrying capacity may be sufficient to supportreconditioning operations.

Operation of the Cell

We describe a range of potential operating modes for a batterymanagement system for a device comprising a gate electrode. In. variousembodiments, there may be a very wide range of operating modes becauseof the very wide range of battery applications with very differentrequirements for safety and power consumption.

The battery management system (BMS) comprises an electronic or softwarecontrol system that controls the battery voltage as it cycles betweencharge and discharge states. A BMS may comprise a manual operatorobserving voltages and currents and causing the application ofappropriate potential differences between selected electrodes to bringthe system to a desired operational state. In its simplestimplementation the BMS may contain no internal electronics: when thevoltage applied across the battery is high enough, the current flows soas to charge the battery; when the voltage drops (i.e., a load isapplied) the battery discharges. However, in the vast majority ofpresent commercial batteries there is some additional electroniccircuitry. The purpose of this electronic circuitry may be, for example,to actively control how rapidly the voltage may increase during charge,or to limit leakage during stand-by or open-circuit operation. A portionof exemplary BMS control circuitry for a small commercial Li-ion cell isshown below from U.S. Pat. No. 6,002,239, although a wide range ofsimilar and related devices may be used. The purpose of the “voltagecomparator” mode in U.S. Pat. No. 6,002,239 is to avoid metal platingand thus non-uniform morphological features in an overvoltage condition.In more complex systems, such as mobile phones or other portableelectronic devices, the BMS may comprise a computer-basedimplementation, such as a PMIC (power management integrated circuit)operating under the control of software (e.g., a set of instructionsrecorded on a machine-readable medium) with current- and voltage-sensingcomponents. In such embodiments, the role of the operator in “observing”currents and voltages can be accomplished by suitable instructionprovided as software or as firmware.

Operating Modes for Devices According to the Invention

We describe an embodiment that uses a manual realization with switches,and briefly outline the extension to automated operation usingelectronic or software controls.

During charge, the risk of device shorting due to non-uniformmorphological features is at its maximum, so the gate current ismonitored closely for shorts. In the event that the current between thecathode and the gate electrode exceeds a predetermined threshold, a“cell health” event may be triggered. In a further implementation thegate voltage may be monitored for a shift away from the targetedpotential. In yet a further implementation, if the voltage response to asense voltage signal between the gate electrode and anode increases(i.e. the resistance decreases) a “cell health” event may be triggered.The trigger voltage, current or resistance may be determined based onthe natural open-circuit voltage of the gate electrode. The open circuitvoltage is a function of the electrochemical potential in theelectrolyte and of the gate electrode materials. Additionally, thetrigger event may be a function of the charging current andstate-of-charge of the anode, and the resistance of a typicalnon-uniform morphological feature in the particular electrochemicalmaterials system. Selection of threshold voltage, current or resistancemay be based on theoretical projections of non-uniform morphologicalfeature behavior or may be based on experience. In yet anotherimplementation, the “triggering current” for a “cell health” event maybe based on empirical studies of the correlation between currentrequired to maintain the gate at target potential and actual cellfailure events in the selected cell, or in a sufficient number ofsimilar devices that a statistical analysis yields a high enoughconfidence level (i.e., 90%, 95%, 99%, 99.9%, or higher). In still afurther implementation, a “cell health” may be assessed based on animpedance or voltage measurement that corresponds to such a triggeringcurrent.

In the event of a “cell health” event being detected, the operator maytrigger one of several possible remedial steps. The simplest remedialstep is to trigger an alarm, terminate the cell charging process, anddiscard the battery. This will prevent a battery from being furthercharged once the current required to maintain the gate at its targetpotential exceeds the threshold, i.e. “cell health” is deemed to havedeteriorated to an unacceptable level. In some embodiments, a controllercomprising a general purpose programmable computer that operates under aset of instructions recorded in a machine-readable medium, oralternatively a dedicated control circuit, may be used in place of ahuman operator.

Alternatively, the recognition of a cell health event may trigger one ofseveral possible “deshorting” steps. One option may be to apply avoltage differential between the gate electrode and the anode that movesthe gate electrode above the stripping potential of the metal. Both thepotential and the duration for which the potential is applied may beadjusted. Another option may be to cease charging and switch the cellinto discharge mode. This discharge step may use a ballast load deviceto dissipate the cell energy. Alternatively the discharge step may usethe discharge of a shorted cell to charge another cell in a battery packcomprising a plurality of cells. The applied deshorting voltage orcurrent may be predetermined so as to bring the gate electrode to therequired voltage even in the presence of a “worst-case” non-uniformmorphological feature. In another implementation, the deshortingprocedure may be determined by finding the voltage (or current or pulseduration) required to achieve a targeted (near-zero) current between thegate electrode and both the anode and the cathode. In yet anotherimplementation, the deshorting procedure may be determined byidentifying the pulse duration (or voltage or current) required toachieve the targeted voltage between the gate electrode and either thecathode or anode (this targeted voltage being close to the open-circuitvoltage for the gate electrode material with respect to the otherelectrode). In still a further implementation, the detection of a shortmay trigger a change in the cycling voltage, so that the cell continuesto cycle but with a modified voltage window. Once the non-uniformmorphological feature is stripped, the current required to maintain thegate electrode at the target voltage will drop to near-zero; howeverafter a shorting event that plates metal onto the gate electrode, itwill frequently be desirable to continue to apply a discharge voltagebetween the gate electrode and the cathode until the gate electrodevoltage reaches its open-circuit potential. In an embodiment involving aplurality of gate electrodes, the deshorting procedure may use one ofmore of the gate electrodes as an anode in the shorting process, so thatstripped metal is sacrificially deposited onto said anode.

During open-circuit operation, the risk of non-uniform morphologicalfeature shorting should be lowered, but it may still be advantageous tomaintain the voltage at the gate electrode while monitoring the currentrequired to maintain voltage. Options for remedial actions in the eventof a short being detected will generally be similar to those taken inthe event of a short during charging (although the circuitimplementation may be different because an external power supply neednot be connected).

During discharge operation, the risk of shorting is again lower thanduring charge, but it may again be advantageous to maintain the gateelectrode at target voltage while monitoring cell health through thecurrent required to maintain potential.

For battery packs utilizing multiple cells the operation of the gateremains roughly unchanged. However, an additional option to monitor cellhealth by measurement of the voltage or current with respect to othercells in the pack is possible. For example either the voltage or thecurrent at a gate electrode may be compared to adjacent gate electrodeseither in the same string or in a string connected in parallel. A cellhealth event can then be triggered by a discrepancy between differentones of otherwise similar gate electrodes. Similarly the remediation mayinclude alarming and discarding the entire pack, alarming and isolatinga single string in a multi-string pack, or discharging a single stringin a pack by charging neighboring strings, in addition to all thesingle-cell remediation approaches discussed above.

Implementation of these operating modes may be through the manualprocess discussed here. Alternatively, a variety of circuit elements maybe used to achieve the same goals (comparing voltages, currents, andresistances and responding by switching voltages, loads and currentswithin the circuit) without manual intervention. The circuit elements ofrelevance in such implementation are well known in the art. Thethresholds for triggering a shorting event (whether measured as any ofcurrents, voltages or resistance) may in such a case be implementedthrough comparison with suitable voltage, current or resistancereferences such as physical references or reference values recorded in amachine-readable medium, or by triggering an active circuit in responseto a voltage or voltage difference, or through some combination thereof.Alternatively, the operating mode may be implemented through a set ofinstructions recorded on a machine-readable medium (i.e., software)operating on an existing BMS or PMIC (most of which already containsufficient physical-layer controls to permit the recognition andresponse or control function discussed herein). The thresholds fortriggering a shorting event (whether measured as any of currents,voltages or resistance) may in a preferred embodiment be stored in alook-up-table held in semiconductor memory.

FIG. 23 illustrates an embodiment of a cell having an anode electrode2340, a cathode electrode 2330, and a gate electrode 2305 whichincorporates a gate structure with separators 2360 and 2370, and anelectrolyte.

We now describe the typical operating conditions for the cellillustrated in FIG. 23. Specifically, the gate 2305 is held high innormal operation such that it does not participate in any plating. Thecharge rate on the cell is limited to ensure high performance, andpreserve the condition of the anode 2340. In a maintenance mode, a smallresting trickle-charge from the gate electrode can be provided byholding the gate electrode approximately 0.1V over the anode voltage.During discharge, the gate electrode 2305 is held approximately 0.1Vbelow the anode so that the gate electrode does not participate in thedischarge.

FIG. 24 shows how the gate electrode can be used to measure cellconditions and controlled to subsequently correct non-uniformmorphological feature formation prior to a catastrophic short-circuit ofthe working electrodes. In particular, during a normal charging phase,the anode operates (see curve segment 2410) at approximately −0.5V,while the gate electrode is held at about 1.5V in an “idle” state (seecurve segment 2420). If a non-uniform morphological feature contacts thegate electrode, the short to the anode drops the voltage closer to theanode voltage (see curve segment 2430). (The actual voltage measured ata shorted gate electrode depends on the resistance of the non-uniformmorphological feature and the resistance of the gate electrode itself).However, this shorts only the gate electrode, not the entire cell, sothere exists the opportunity to apply a negative voltage to the gateelectrode to “strip” down the non-uniform morphological feature (seecurve segment 2440). Once this is done, the normal charging of the cellcan continue (see curve segment 2450). This process can be repeated manytimes (see curve segment 2460) to extend the life of the cell and tooperate the cell safely.

FIG. 25A illustrates a method of recognizing an incipient cell short,and responding to such detection with a reconditioning step, and theresistance requirements for the proposed gate electrode versus theaffected working electrode. In FIG. 25A there is depicted anelectrochemical cell 2500 having a gate electrode 2505 that is both gateelectrode is both electrolytically and electrically conductivecomprising a support 2510 that is ionically conducting and anelectrically conductive layer 2520 provided on the support. The gate2505 has a gate electrode electrical terminal 2507 that can be accessedfrom the exterior of the cell. The cell 2500 in FIG. 25A has a cathode2530 and an anode 2540 that are separated by the gate electrode 2505.Electrolyte 2550′, 2550″ is provided between the cathode 2530 and theanode 2540. Gate 2505 is immersed in the electrolyte. A non-uniformmorphological feature 2560 is illustrated.

FIG. 25B schematically illustrates the gate electrode resistanceR_(gate) and the resistance of a non-uniform morphological featureR_(numf). In order to efficiently strip non-uniform morphologicalfeatures the resistance of the gate electrode preferably should be lowerthan that of the non-uniform morphological feature. Power is given byI²R, or by V²/R, where I is current, V is voltage and R is resistance. Acommon stripping current will be caused to flow through the gateelectrode and the non-uniform morphological feature. If R_(numf) islarger than R_(gate) the power necessary to strip the non-uniformmorphological feature is dissipated in the non-uniform morphologicalfeature, and much less power is dissipated in the gate itself. In apreferred embodiment, R_(gate) is less than 1 kOhm resistance.

FIG. 26 is a flow chart illustrating the operating method for amulti-electrode electrochemical (MEE) cell protected according to thepresent disclosure. In general, if there are N electrodes in themulti-electrode electrochemical cell, where N is an integer greater thanor equal to 3, N−1 control circuits can be employed to actively controlthe current and voltage relationships among the N electrodes. Theprocess starts at step 2610. In step 2612, the active control circuitchecks to see if the cell is or is not at idle (e.g., is disconnectedfrom an operating apparatus that uses the cell as a current or voltagesource or sink, and exhibits appropriate electrical parameters that arenot varying with time). If the cell is at idle, the process performs await cycle 2614 and goes back to step 2612. If the controller determinesthat the cell is not at idle (i.e., that the cell is operating, or thatthe cell electrical parameters are changing with time), the processproceeds to step 2620, and the active control circuit measures the N−1current/voltage relationships that exist among the N electrodes.

In step 2630, the N−1 measured current/voltage relationships arecompared to entries in a table (or are compared to hard wired current orvoltage references, or some combination of such comparisons isperformed).

In step 2632, the active control circuit determines the cell state,which can be any one of normal operation with charging (represented bybox 2640), normal operation with discharging (represented by box 2650),and a state in which stripping of non-uniform morphological features isappropriate (represented by box 2660).

In box 2640, the controller causes the MEE cell to be charged by passinga current between the anode and the cathode, or alternatively, byapplying a voltage between the anode and the cathode.

In box 2650, the controller permits the MEE cell to be discharged bycontrolling (or limiting) a current that flows between the anode and thecathode, or alternatively, by controlling (or limiting) a voltagebetween the anode and the cathode.

In box 2660, the controller applies a current or a voltage between agate electrode and one of the anode and the cathode in order to cause anon-uniform morphological feature to be “stripped” or dissolved.

Each of the processes represented by boxes 2640, 2650 and 2660 can bemaintained for a predetermined interval, which can be dependent on thestate of the MEE cell, or can be a default interval of time sufficientto cause a predefined amount of charge to pass a terminal of a specificelectrode (e.g., a pulse duration or a number of cycles of a periodicfunction).

From time to time, the control circuit returns via path 2670 to step2612, and the then current state of the multi-electrode electrochemicalcell is again evaluated. The process can be iterated as many times asdesired or as may be useful to maintain the MEE cell in a desired state.

The method embodied in FIG. 26 may be implemented manually, or by otherwell known methods such as the use of a controller described below.

FIG. 29A is a graph of the cell voltage (i.e., the voltage measuredbetween the positive and negative cell terminals) as a function of timefor a rechargeable Li metal secondary cell wherein the N/P capacityratio ≦1.

FIG. 29B is a graph that depicts the gate voltage (i.e., the voltagemeasured between the gate and negative cell terminals) as a function oftime for a rechargeable Li metal secondary cell wherein the N/P capacityratio ≦1. Note the gated cell depicted here is under active controlwherein the bias is set at about 0.5 V.

Deviation of the gate voltage from the nominal value is represented asthe voltage “spikes.” This deviation corresponds to an increase in anodepotential at the end of discharge due to depletion of Li from thenegative electrode. The control circuit recognizes the response of thegate potential and responds by driving oxidative current necessary tocorrect the gate potential vs. the negative electrode, so as to maintainthe desired operating conditions and corresponding state of health.

In another non-limiting example of active control embodiment FIG. 30depicts the cathode energy density as a function of cycle number forgated rechargeable Li metal secondary cell wherein the N/P capacityratio ≦1. Note the gated cells depicted here are under active controlwherein the gate bias is set at either 0.5 V, 2.5 V, or 3.5 V. The gatepotential is controlled vs. the negative electrode in this example, sothat the gate electrode may impose oxidative or reductive current inorder to maintain the desired gate potential set point. This dataindicates that key performance criteria of the cell such as energydensity and capacity fade are directly influenced by the method ofactive control of the gate.

FIG. 31 depicts the average charge and discharge voltage as a functionof cycle number for the gated rechargeable Li metal secondary cellwherein the N/P capacity ratio ≦1 depicted in FIG. 30. Note the gatedcells depicted here are under active control wherein the bias is set ateither 0.5 V, 2.5 V, or 3.5 V. The data depicted in FIG. 31 indicatesthat the active control of the gate potential directly influences theaverage charge and discharge potential of the cells. Consequently forthe cell chemistry and design depicted in FIG. 30 and FIG. 31, applyingactive control set point of the gate to 0.5 V vs. the negative electrodemaintains favorable average cell potential for more cycles than whensetting the gate potential to 2.5 V or 3.5 V.

In yet another embodiment of active control FIG. 32 depicts the chargeand discharge voltage as a function of cycle number for gatedrechargeable Li metal secondary cell wherein the N/P capacity ratio ≦1.Note the gated cells depicted herein are under active control whereinthe gate potential changing to −2.6 V vs. the negative electrodesignifies optimal depletion of the active material from the negativeelectrode. Upon recognition of this event the control circuit responds,triggering end of cell discharge. The cell then proceeds to the nextstep in the operation sequence; in this case initiate charge. The gatepotential is controlled vs. the negative electrode in this example.

FIG. 33 is an image of a test apparatus 3300 for operating a cellaccording to the present disclosure, which incorporates a gateelectrode. As seen in FIG. 33, a Cell 3305 has a negative electrode witha negative terminal 3310, a positive electrode with a positive terminal3315, a gate terminal 3320 which is connected to a limiting resistor,and which is in electrical communication with test apparatus comprisinga test charger 3325 and an external voltage supply 3330 that is used toset a voltage of the gate electrode relative to one of the negativeelectrode and the positive electrode. Note that the gate itselfcomprises about 100 nm of gold-palladium alloy sputtered onto porouspolyolefin separator connected to a tab via ultrasonic weld.

Method of Periodic Dendrite Dissolution

FIG. 27 is a flow chart illustrating an alternative operating method fora cell protected according to the present disclosure, using acontroller. In the process shown in FIG. 27, the cell is periodicallyoperated in a manner calculated to dissolve dendrites that may havebegun to grow from one of the anode electrode or the cathode electrode,and can be applied even before an incipient short circuit is detected.In some embodiments, this method may, for example be applied to abattery during a period when it is expected that the battery will not berequired to be used in a specific application, such as a time when amachine is scheduled to be out of operation (e.g., an automobile sittingparked in a garage in a home overnight, an aircraft parked at an airportovernight, or the like).

The process starts at step 2710. When the cell is first turned on in acharge mode, a timer is activated in the controller, and the cumulativeduration of charge is measured. The controller records the cumulativeduration of charge from the first turn on along with the currentrequired to maintain the gate at target potential.

For a given model of secondary battery, one can build a database overtime that includes the charge interval needed to reach a criticalcell-health condition in individual secondary batteries of that modelare recorded. Over time, one can determine with a numerical confidencelevel a charge time T₁ after which a shorting event is likely to occur.

For example, one might determine that a charge duration of T₀ hours willresult in the presence of a short across the secondary battery with aconfidence of 95%. One could then set a duration T₁=0.9×T₀ as a durationat which a discharge step or a stripping step might reasonably beinstituted so as to avoid the likelihood that a short condition mightoccur. In principle, a shorter duration can be set if the consequence ofa short occurring would be more serious, and a longer duration can beset if the consequence of a short occurring would be less serious.

In step 2712 the control compares the cumulative duration of charge fromthe first turn on against a recorded value of T₀ and determines ifduration T₁ has elapsed. If the duration T₁ has not elapsed, thecontroller passes control to step 2714. If duration T₁ has elapsed, thecontroller passes control to via arrow 2730 to step 2740.

In step 2714 the controller waits and checks again after a waitingperiod, which waiting period preferably is a short interval compared tothe value of T₁. The process then moves along arrow 2716 back to step2712.

In step 2740 the controller institutes a stripping or discharge step,after making sure that taking the monitored secondary battery out ofoperation will not present a problem. The stripping or discharge stepcan be operated for a duration calculated to dissolve dendrites.

Upon completion of step 2740 the controller moves the process to step2760 by way of arrow 2750.

In step 2760 the controller resets recorded value of T₀ to zero.

Upon completion of step 2760 the controller moves the process to step2712 by way of arrow 2770.

The process can then repeat for that secondary battery. The process canbe performed for each secondary battery in an array, so that nosecondary battery runs a reasonable chance of reaching a shorted state.Since the process is statistical, no measurement of the state of thesecondary battery as regards a shorting condition needs to be performed.

The same principles for managing cells can be extended to batteriescomposed from one or more cells.

Description of the Controller

U.S. Pat. No. 6,002,239 describes several embodiments of circuits thatcan control the voltage applied between a cathode and an anode of arechargeable battery. U.S. Pat. No. 6,002,239 does not describe abattery having a gate electrode in addition to the cathode and theanode. U.S. Pat. No. 6,002,239 does not describe a circuit that controlsthe respective relative voltage between a cathode and a gate electrodeor the relative voltage between an anode and a gate electrode in abattery having a gate electrode in addition to the cathode and theanode.

In the present application one needs a circuit that controls thecurrent-voltage relationship among each pair of electrodes, e.g. betweenthe anode and the gate electrode, between the cathode and the gateelectrode, and between the cathode and the anode. In some embodiments,setting two of the three current-voltage relationships is sufficient,because the third relationship will then be determined.

FIG. 28 is a schematic of one prior art control circuit (presented inU.S. Pat. No. 6,002,239 as FIG. 2 thereof and described in detailtherein) that can be used to operate a multi-electrode electrochemicalcell according to the present disclosure. In some embodiments, twocontrol circuits as illustrated in FIG. 28 can be used by connectingterminal 2 of each circuit to a single electrode selected from theanode, the cathode and the gate electrode of a multi-electrodeelectrochemical cell, connecting terminal 3 of one control circuit toanother of the anode, the cathode and the gate electrode of themulti-electrode electrochemical cell, and connecting terminal 3 of theother control circuit to the remaining one of the anode, the cathode andthe gate electrode of the multi-electrode electrochemical cell. In thecircumstance that additional (i.e., more than two) gate electrodes areprovided within the multi-electrode electrochemical cell, each suchadditional gate electrode can be independently controlled by anadditional control circuit such as shown in FIG. 28. In otherembodiments, control circuits as shown in FIG. 1 and FIG. 3 of U.S. Pat.No. 6,002,239 can also be employed.

While FIG. 28 shows an embodiment that relies on a hard-wiredimplementation, one can modify a circuit such as shown in FIG. 28 toallow manual operation by an operator, which may require a display orannunciator to provide the operator with information that representssome or all of the measured current-voltage relationships determined instep 2620. In another alternative embodiment, the controller cancomprise a general purpose programmable computer that operates under thecontrol of instructions recorded on a machine-readable medium.

DEFINITIONS

As used in the present application, the term “cell health” is to beunderstood as a descriptor of the physical condition of a cell, such as“normal cell health” to describe a cell having normal operatingparameters.

As used in the present application, the term “cell health event” is tobe understood as denoting a condition in which a cell of the inventiondeviates from one having “normal cell health.” Examples include a cellexhibiting a higher than normal current required to maintain a gateelectrode at a predetermined potential, a cell exhibiting a voltagebetween a gate electrode and either of an anode electrode or a cathodeelectrode that is lower than a threshold voltage, or a cell exhibiting aresistance between a gate electrode and either of an anode electrode ora cathode electrode that is lower than a threshold value.

As used in the present application, the term “non-uniform morphology,”whether used in the singular or plural form, is to be understood asreferring to any of an asperity, a dendrite, a whisker, a roughness of asurface, an unevenness of a surface, an object that forms a projection,a warping of a surface, a swelling from a surface, or the like. Theserecited examples are not meant to be exclusive, but to convey theunderstanding that the term “non-uniform morphology” relates to manydifferent types of irregularities of shape of an electrode surface thatcan come to pass as a battery is operated, or as a battery ages.

As used in the present application, the term “active electrode” is to beunderstood as an electrode that can in normal operation aftermanufacturing be operated by an external device, such as a power supplyor a controller, so that the electrode is obliged to assume a currentand/or voltage condition that is imposed upon it by the power supplyand/or the controller. In contradistinction, the term “passiveelectrode” is to be understood as an electrode that assumes a currentand/or voltage condition as a consequence of the normal operation aftermanufacturing of an electrochemical cell as a function of time, andwhich current and/or voltage condition is not imposed upon it by a powersupply and/or a controller. It is further to be understood that while aspecific electrode may at some times be considered an “active electrode”and at other times a “passive electrode”, any electrode that isdescribed or is understood to be an “active electrode” at any time innormal operation after manufacturing is categorized as an “activeelectrode.” That is to say that an “active electrode” may not becontrolled at all times, but a “passive electrode” is never controlledin normal operation after manufacturing.

As used in the present application, the term “Mg cell” or “Mg battery”is to be understood as referring to an electrochemical cell in which theredox-active species in an electrolyte comprises magnesium (Mg) inwhatever form, such as a metal, an ion, a salt, a chelate, and acompound.

Unless otherwise explicitly recited herein, any reference to anelectronic signal or an electromagnetic signal (or their equivalents) isto be understood as referring to a non-volatile electronic signal or anon-volatile electromagnetic signal.

Recording the results from an operation or data acquisition, such as forexample, recording results at a particular frequency or wavelength, isunderstood to mean and is defined herein as writing output data in anon-transitory manner to a storage element, to a machine-readablestorage medium, or to a storage device. Non-transitory machine-readablestorage media that can be used in the invention include electronic,magnetic and/or optical storage media, such as magnetic floppy disks andhard disks; a DVD drive, a CD drive that in some embodiments can employDVD disks, any of CD-ROM disks (i.e., read-only optical storage disks),CD-R disks (i.e., write-once, read-many optical storage disks), andCD-RW disks (i.e., rewriteable optical storage disks); and electronicstorage media, such as RAM, ROM, EPROM, Compact Flash cards, PCMCIAcards, or alternatively SD or SDIO memory; and the electronic components(e.g., floppy disk drive, DVD drive, CD/CD-R/CD-RW drive, or CompactFlash/PCMCIA/SD adapter) that accommodate and read from and/or write tothe storage media. Unless otherwise explicitly recited, any referenceherein to “record” or “recording” is understood to refer to anon-transitory record or a non-transitory recording.

As is known to those of skill in the machine-readable storage mediaarts, new media and formats for data storage are continually beingdevised, and any convenient, commercially available storage medium andcorresponding read/write device that may become available in the futureis likely to be appropriate for use, especially if it provides any of agreater storage capacity, a higher access speed, a smaller size, and alower cost per bit of stored information. Well known oldermachine-readable media are also available for use under certainconditions, such as punched paper tape or cards, magnetic recording ontape or wire, optical or magnetic reading of printed characters (e.g.,OCR and magnetically encoded symbols) and machine-readable symbols suchas one and two dimensional bar codes. Recording image data for later use(e.g., writing an image to memory or to digital memory) can be performedto enable the use of the recorded information as output, as data fordisplay to a user, or as data to be made available for later use. Suchdigital memory elements or chips can be standalone memory devices, orcan be incorporated within a device of interest. “Writing output data”or “writing an image to memory” is defined herein as including writingtransformed data to registers within a microcomputer.

“Microcomputer” is defined herein as synonymous with microprocessor,microcontroller, and digital signal processor (“DSP”). It is understoodthat memory used by the microcomputer, including for exampleinstructions for data processing coded as “firmware” can reside inmemory physically inside of a microcomputer chip or in memory externalto the microcomputer or in a combination of internal and externalmemory. Similarly, analog signals can be digitized by a standaloneanalog to digital converter (“ADC”) or one or more ADCs or multiplexedADC channels can reside within a microcomputer package. It is alsounderstood that field programmable array (“FPGA”) chips or applicationspecific integrated circuits (“ASIC”) chips can perform microcomputerfunctions, either in hardware logic, software emulation of amicrocomputer, or by a combination of the two. Apparatus having any ofthe inventive features described herein can operate entirely on onemicrocomputer or can include more than one microcomputer.

General purpose programmable computers useful for controllinginstrumentation, recording signals and analyzing signals or dataaccording to the present description can be any of a personal computer(PC), a microprocessor based computer, a portable computer, or othertype of processing device. The general purpose programmable computertypically comprises a central processing unit, a storage or memory unitthat can record and read information and programs using machine-readablestorage media, a communication terminal such as a wired communicationdevice or a wireless communication device, an output device such as adisplay terminal, and an input device such as a keyboard. The displayterminal can be a touch screen display, in which case it can function asboth a display device and an input device. Different and/or additionalinput devices can be present such as a pointing device, such as a mouseor a joystick, and different or additional output devices can be presentsuch as an enunciator, for example a speaker, a second display, or aprinter. The computer can run any one of a variety of operating systems,such as for example, any one of several versions of Windows, or ofMacOS, or of UNIX, or of Linux. Computational results obtained in theoperation of the general purpose computer can be stored for later use,and/or can be displayed to a user. At the very least, eachmicroprocessor-based general purpose computer has registers that storethe results of each computational step within the microprocessor, whichresults are then commonly stored in cache memory for later use, so thatthe result can be displayed, recorded to a non-volatile memory, or usedin further data processing or analysis.

Many functions of electrical and electronic apparatus can be implementedin hardware (for example, hard-wired logic), in software (for example,logic encoded in a program operating on a general purpose processor),and in firmware (for example, logic encoded in a non-volatile memorythat is invoked for operation on a processor as required). The presentinvention contemplates the substitution of one implementation ofhardware, firmware and software for another implementation of theequivalent functionality using a different one of hardware, firmware andsoftware. To the extent that an implementation can be representedmathematically by a transfer function, that is, a specified response isgenerated at an output terminal for a specific excitation applied to aninput terminal of a “black box” exhibiting the transfer function, anyimplementation of the transfer function, including any combination ofhardware, firmware and software implementations of portions or segmentsof the transfer function, is contemplated herein, so long as at leastsome of the implementation is performed in hardware.

THEORETICAL DISCUSSION

Although the theoretical description given herein is thought to becorrect, the operation of the devices described and claimed herein doesnot depend upon the accuracy or validity of the theoretical description.That is, later theoretical developments that may explain the observedresults on a basis different from the theory presented herein will notdetract from the inventions described herein.

Any patent, patent application, patent application publication, journalarticle, book, published paper, or other publicly available materialidentified in the specification is hereby incorporated by referenceherein in its entirety. Any material, or portion thereof, that is saidto be incorporated by reference herein, but which conflicts withexisting definitions, statements, or other disclosure materialexplicitly set forth herein is only incorporated to the extent that noconflict arises between that incorporated material and the presentdisclosure material. In the event of a conflict, the conflict is to beresolved in favor of the present disclosure as the preferred disclosure.

While the present invention has been particularly shown and describedwith reference to the preferred mode as illustrated in the drawing, itwill be understood by one skilled in the art that various changes indetail may be affected therein without departing from the spirit andscope of the invention as defined by the claims.

What is claimed is:
 1. A device comprising: a cathode electrode having acathode electrical terminal, said cathode electrode in electrochemicalcommunication with an electrolyte; an anode electrode having a anodeelectrical terminal, said anode electrode in electrochemicalcommunication with said electrolyte; at least one gate electrode havinga gate electrode electrical terminal, said at least one gate electrodein electrochemical communication with said electrolyte and permeable toat least one mobile species which is redox-active at at least one ofsaid anode electrode and said cathode electrode, said at least one gateelectrode situated between said cathode electrode and said anodeelectrode; and a control circuit configured to actively control anoperating parameter of the device.
 2. The device of claim 1, whereinsaid control circuit is configured to set a voltage of said at least onegate electrode relative to at least one of said anode electrode and saidcathode electrode at a predetermined voltage value.
 3. The device ofclaim 2, wherein said predetermined voltage value is sufficient to stripplated metal derived from said at least one mobile species.
 4. Thedevice of claim 2, wherein said predetermined voltage value is aformation potential of a non-uniform morphological feature.
 5. Thedevice of claim 1, wherein said control circuit is configured tomaintain a current between said at least one gate electrode and saidanode electrode to be less than a threshold current.
 6. The device ofclaim 1, wherein said control circuit is configured to control a flow ofcurrent through said device based on one of a voltage, an impedance anda current measured between said at least one gate electrode and at leastone of said anode electrode and said cathode electrode.
 7. The device ofclaim 1, wherein said device is a secondary electrochemical cell.
 8. Thedevice of claim 1, wherein said at least one gate electrode has a planargeometry defined by a thickness dimension and a two dimensional areaperpendicular to said thickness dimension.
 9. The device of claim 8,wherein said at least one gate electrode is ionically conductive alongsaid thickness dimension and is electrically conductive perpendicular tosaid thickness dimension.
 10. The device of claim 1, wherein animpedance measured at a frequency less than 1 Hertz between any twopoints on a two dimensional area perpendicular to said thicknessdimension of said at least one gate electrode is less than 1 MegaOhm.11. The device of claim 1 wherein said anode electrode is a metal anode.12. The device of claim 11 wherein said metal anode is Magnesium or analloy containing Magnesium.
 13. The device of claim 11 wherein saidmetal anode comprises a metal or an alloy containing a metal selectedfrom the group of metals consisting of Zinc, Calcium, Aluminum, Lithium,Sodium, and Lead.
 14. The device of claim 1 wherein said anode electrodeis an anode electrode selected from the group consisting of a conversionanode, an intercalation host, an alloying reaction anode and adisproportionation reaction anode.
 15. The device of claim 1 wherein theredox-active ionic species is lithium and said anode comprises amaterial selected from the group of materials consisting of crystallinecarbon, amorphous carbon, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Al, Si, Ge, Sb,Pb, In, Zn, Sn, and binary Me-×compounds wherein X is selected from thegroup consisting of sulfur, phosphorous, nitrogen and oxygen, and Meincludes a metal selected from the group consisting of Mg, Ca, Sr, Ti,Zr, V, Nb, Ta, Cr, Mo, W, Mn, Fe, Co, Ni, Cu, Ag, Zn, Cd, B, Al, Si, Sn,Ge, Sb, Bi and a combination thereof.
 16. The device of claim 1, whereinsaid anode electrode is configured to operate under plating conditionsbased on the temperature, voltage, charging-rate or combination thereof.17. The device of claim 1, wherein said at least one gate electrodecomprises a selected one of an electronically conducting material asfreestanding form and an electronically conductive film deposited uponan insulating substrate having porosity and tortuosity, and connected toexternal circuit through a dedicated tab.
 18. The device of claim 1wherein said at least one gate electrode has porosity sufficient tomaximize the efficiency of said permeability to said at least one mobilespecies.
 19. The device of claim 1 wherein said at least one gateelectrode has porosity having sufficient tortuosity to minimize theprobability that a non-uniform morphological feature projecting throughsaid at least one gate electrode fails to make electrical contact tosaid at least one gate electrode.
 20. A secondary electrochemical cellhaving a cathode electrode having a cathode electrical terminal, saidcathode electrode in electrochemical communication with a electrolyteand an anode electrode having a anode electrical terminal, said anodeelectrode in electrochemical communication with said electrolyte;wherein the improvement comprises: at least one gate electrode having agate electrode electrical terminal, said at least one gate electrode inelectrochemical communication with said electrolyte and permeable to atleast one mobile species in said electrolyte which is redox-active at atleast one of said anode electrode and said cathode electrode, said atleast one gate electrode situated between said cathode electrode andsaid anode electrode; and a control circuit configured to activelycontrol an operating parameter of the device.
 21. A method of making anelectrochemical device, comprising the steps of: providing a cathodeelectrode having a cathode electrical terminal; providing an anodeelectrode having a anode electrical terminal; providing an electrolytein in electrochemical communication with said cathode electrode and saidanode electrode; providing at least one gate electrode having a gateelectrode electrical terminal, said at least one gate electrode inelectrochemical communication with said electrolyte and permeable to atleast one mobile species in said anode electrode which is redox-activeat at least one of said anode electrode and said cathode electrode, saidat least one gate electrode situated between said cathode electrode andsaid anode electrode; and providing a control circuit configured toactively control an operating parameter of the device.
 22. A method ofoperating an electrochemical device, comprising the steps of: providinga cathode electrode having a cathode electrical terminal; providing ananode electrode having a anode electrical terminal; providing anelectrolyte in in electrochemical communication with said cathodeelectrode and said anode electrode; providing at least one gateelectrode having a gate electrode electrical terminal, said at least onegate electrode in electrochemical communication with said electrolyteand permeable to at least one mobile species in said anode electrodewhich is redox-active at at least one of said anode electrode and saidcathode electrode, said at least one gate electrode situated betweensaid cathode electrode and said anode electrode; providing a controlcircuit configured to actively control an operating parameter of thedevice; and operating said electrochemical device such that said controlcircuit maintains said operating parameter of said electrochemicaldevice in a condition of normal cell health.